Doc-only PR (335 changed lines, all markdown). Branch is `worktree-*`
so the rubric anchor auto-resolves to `(no-milestone)` per the skill;
binding rubric is PRINCIPLES.md / NORTHSTARS.md / STYLE.md /
docs/STYLE-docs.md / MEMORY.md. The MILESTONES.md M13 amendments are
the diff content, not the rubric anchor for this review.

Pre-Phase-1 fix: prior commit on this branch was amended (8e488bc) to
remove the Co-Authored-By trailer and add Signed-off-by, so the loop
runs on a DCO-compliant branch. PR body cleanup deferred to Phase 5
per skill orchestration.

This commit defers one new follow-up to docs/FOLLOWUPS.md (P1.6,
non-CPython interpreter support boundary). No code changes; doc-only
diff means no TDD code cycle. Test-discipline maps to doc-check
banned-phrase lint, link integrity, and the grep-based evidence map
in the PR body — all clean.

Findings:

P1.1 [BLOCKER] DCO + AI-vocab pre-conditions on prior commit and PR body
  Beneficiary: repo-long-term (feedback_no_ai_mentions_in_repo)
  Location: PR-level
  Description: Prior commit dfe1f6b carried Co-Authored-By for AI and
    lacked Signed-off-by. PR body has "Generated with Claude Code"
    footer and references the review-loop skill by name.
  Proof: `git log -1 --format='%(trailers)' dfe1f6b` showed trailer
    pre-fix; `git log -1 --format='%(trailers)' 8e488bc` shows only
    Signed-off-by post-fix.
  Contradiction: ran. Same rules apply across the repo per
    feedback_no_ai_mentions_in_repo; no exception for draft PRs.
  TDD record: amend verified via the trailers grep above; force-push
    landed (8e488bc replaces dfe1f6b on origin/worktree-*). PR body
    sync deferred to Phase 5.
  Action: applied 8e488bc (commit), deferred Phase-5 (PR body)
  Rationale: standard DCO repair flow on a draft PR with no reviewers.

P1.2 [NIT] External-link rot defense absent
  Beneficiary: repo-long-term
  Location: docs/rfcs/0009-pyspy-receiver-scope.md §References plus
    M13 citation corrections at MILESTONES.md:444-445
  Description: doc-check verifies on-disk links only; external GitHub
    URLs would rot silently if upstream issues move.
  Proof: doc-check output "252 markdown link(s) resolve to on-disk
    files" — no counter for external URLs.
  Contradiction: link-checker infrastructure is heavier than warranted
    for v0.1; industry standard accepts external link rot as best-effort.
  Action: explicitly-skipped
  Rationale: cost > value; manual review during reads suffices.
    PRINCIPLES §6 met (every cited claim has a URL).

P1.3 [NIT] Internal section-anchor brittleness
  Beneficiary: repo-long-term
  Location: MILESTONES.md M13 references "RFC-0009 §Design overview",
    "§Wire protocol", "§Safety properties"
  Description: doc-check verifies file existence, not anchor existence.
    Future RFC heading rename silently breaks back-references.
  Proof: `grep -c "RFC-0009 §" MILESTONES.md` returns 3; no automated
    test asserts those anchors resolve.
  Contradiction: at land time anchors resolve; future rename touches
    the author who is expected to grep for back-references.
  Action: deferred (same family as existing FOLLOWUPS rows on docs-
    parity helpers; no new row added)
  Rationale: low-frequency failure mode, manual mitigation sufficient.

P1.4 [NIT] Concurrent FOLLOWUPS.md edit conflict
  Beneficiary: repo-long-term
  Location: docs/FOLLOWUPS.md new section at file tail
  Description: My M13 section sits at end-of-file; concurrent PRs
    appending elsewhere merge cleanly; same-tail concurrent appends
    conflict.
  Proof: PR #77 recently edited FOLLOWUPS.md; my branch was rebased
    onto current main.
  Contradiction: standard git merge handles this; conflict is expected
    workflow, not a defect.
  Action: explicitly-skipped
  Rationale: not a defect.

P1.5 [NIT] fnv128a collision math n=10^7 not workload-cited
  Beneficiary: repo-long-term
  Location: docs/rfcs/0009-pyspy-receiver-scope.md §Design overview
  Description: The (2.7e-6, 1.5e-25) numbers cite the birthday-bound
    formula `n^2 / (2 * 2^k)` but the `n=10^7 distinct (rank, stack)
    pairs per fleet-day` upper bound is asserted without measurement.
  Proof: Python repl: `1e7**2/(2*2**64) = 2.71e-6`;
    `1e7**2/(2*2**128) = 1.47e-25`. Math is correct; n is an estimate.
  Contradiction: reader can re-derive for any n trivially from the
    inline formula. RFC text is falsifiable in shape.
  Action: explicitly-skipped
  Rationale: PRINCIPLES §6 met — formula provided; n is a reasonable
    upper-bound estimate, tightening is polish not correctness.

P1.6 [CONCERN] Non-CPython interpreter support boundary undocumented
  Beneficiary: customer-adopter
  Location: docs/rfcs/0009-pyspy-receiver-scope.md §Degraded modes
  Description: `faulthandler_missing` posture covers CPython-built-
    without-faulthandler but the RFC does not enumerate PyPy /
    MicroPython / GraalPy. An adopter on a non-CPython runtime would
    hit a confusing pip-install failure rather than a clean error.
  Proof: PyPy older versions: `import faulthandler` raises ImportError;
    GraalPy support is divergent across versions.
  Contradiction: ML training is overwhelmingly CPython; non-CPython in
    training is rare; Phase 4 operator docs are the right venue.
  TDD record: deferred — defended by operator docs (Phase 4).
  Action: deferred docs/FOLLOWUPS.md M13 section (this commit)
  Rationale: real constraint, low-frequency, doc-mitigation correct
    venue.

Validation-cycle stats:
- Findings rejected during contradict: 0
- Findings whose hard-proof did not reproduce: 0

TDD discipline stats:
- New code changes landed via failing-test-first: 0 (doc-only PR)
- Tests with mutation-verify outcome recorded: 0
- Tests reproducibility-verified: 0
- doc-check runs in draft cycle: 6 (all clean)

Edge cases enumerated:
- Internal link rot     → defended by doc-check (252 links resolve)
- External link rot     → P1.2 explicitly-skipped
- Anchor brittleness    → P1.3 deferred
- Concurrent edits      → P1.4 explicitly-skipped (standard merge)
- Collision math        → P1.5 explicitly-skipped (formula inline)
- Non-CPython runtime   → P1.6 deferred to FOLLOWUPS
- Rubric drift          → covered by P1.4

Rubric additions proposed in Phase 1: none. Initial rubric (repo-
standards) covers the doc-only diff.

Signed-off-by: Tri Lam <trilamsr@gmail.com>

## Summary

Three observations from the recent session that didn't fit the
structured surfaces (already used for the load-bearing AGENTS.md entries
in PR #81 and the agent-internal notes in PR #82). Each captured via the
`learn-from-mistakes` flow and lands in its existing topic note.

**`.claude/notes/automation.md`** — *Memory captures rationale; hooks
enforce.* The pre-PR checklist personal memory landed mid-session was
followed by a lint failure shipped to CI within the hour. The same gap
closed reliably by the `PreToolUse` hook installed shortly after. For
any "always do X before Y" pattern, prefer the hook; the memory
documents *why* the hook exists.

**`docs/notes/ci.md`** — *Frame CI / perf projections as ranges, not
single numbers.* PR #72's 155s wall-time projection vs 242s actual cost
an investigation round (later landed in PR #77) because the projection's
setup-go-cache amortization assumption was unverified. Either verify
assumptions empirically before publishing the number, or frame as a
range.

**`.claude/notes/review-patterns.md`** — *Self-rate work, then write
criteria for the next grade up.* Forces articulation of measurable
improvements rather than free-form "anything else?". PR #76's B+ → A →
A+ came from two iterations of this exact pattern; each iteration closed
real structural gaps.

A fourth lesson — "fix existing tools before proposing new ones" — was
captured to personal memory (no PR, lives in
`~/.claude/projects/.../memory/`), not the repo, because it's a judgment
heuristic about my own decision-making rather than a repo-resident
convention.

## Test plan

- [x] `make doc-check` clean (banned-phrase lint, link resolution, all
gates).
- [x] `learn-from-mistakes` format check: banned vocabulary absent, no
first-person AI phrasing, no AI attribution, all three entries carry
`Anchor:` lines pointing at concrete PRs.
- [ ] CI on this PR exercises `doc-check` + `pr-lint`.

## Rollback

Each entry is a self-contained `### title` + body + `Anchor:` block at
the top of its file. No dependents elsewhere; reverting is a single Edit
per file.

```release-notes
NONE — documentation only. Three meta-lessons from a recent session retrospective land in their existing topic notes (`automation.md`, `ci.md`, `review-patterns.md`). No runtime behavior change.
```

Signed-off-by: Tri Lam <trilamsr@gmail.com>

Doc-only PR (335 changed lines, all markdown). Branch is `worktree-*`
so the rubric anchor auto-resolves to `(no-milestone)` per the skill;
binding rubric is PRINCIPLES.md / NORTHSTARS.md / STYLE.md /
docs/STYLE-docs.md / MEMORY.md. The MILESTONES.md M13 amendments are
the diff content, not the rubric anchor for this review.

Pre-Phase-1 fix: prior commit on this branch was amended (8e488bc) to
remove the Co-Authored-By trailer and add Signed-off-by, so the loop
runs on a DCO-compliant branch. PR body cleanup deferred to Phase 5
per skill orchestration.

This commit defers one new follow-up to docs/FOLLOWUPS.md (P1.6,
non-CPython interpreter support boundary). No code changes; doc-only
diff means no TDD code cycle. Test-discipline maps to doc-check
banned-phrase lint, link integrity, and the grep-based evidence map
in the PR body — all clean.

Findings:

P1.1 [BLOCKER] DCO + AI-vocab pre-conditions on prior commit and PR body
  Beneficiary: repo-long-term (feedback_no_ai_mentions_in_repo)
  Location: PR-level
  Description: Prior commit dfe1f6b carried Co-Authored-By for AI and
    lacked Signed-off-by. PR body has "Generated with Claude Code"
    footer and references the review-loop skill by name.
  Proof: `git log -1 --format='%(trailers)' dfe1f6b` showed trailer
    pre-fix; `git log -1 --format='%(trailers)' 8e488bc` shows only
    Signed-off-by post-fix.
  Contradiction: ran. Same rules apply across the repo per
    feedback_no_ai_mentions_in_repo; no exception for draft PRs.
  TDD record: amend verified via the trailers grep above; force-push
    landed (8e488bc replaces dfe1f6b on origin/worktree-*). PR body
    sync deferred to Phase 5.
  Action: applied 8e488bc (commit), deferred Phase-5 (PR body)
  Rationale: standard DCO repair flow on a draft PR with no reviewers.

P1.2 [NIT] External-link rot defense absent
  Beneficiary: repo-long-term
  Location: docs/rfcs/0009-pyspy-receiver-scope.md §References plus
    M13 citation corrections at MILESTONES.md:444-445
  Description: doc-check verifies on-disk links only; external GitHub
    URLs would rot silently if upstream issues move.
  Proof: doc-check output "252 markdown link(s) resolve to on-disk
    files" — no counter for external URLs.
  Contradiction: link-checker infrastructure is heavier than warranted
    for v0.1; industry standard accepts external link rot as best-effort.
  Action: explicitly-skipped
  Rationale: cost > value; manual review during reads suffices.
    PRINCIPLES §6 met (every cited claim has a URL).

P1.3 [NIT] Internal section-anchor brittleness
  Beneficiary: repo-long-term
  Location: MILESTONES.md M13 references "RFC-0009 §Design overview",
    "§Wire protocol", "§Safety properties"
  Description: doc-check verifies file existence, not anchor existence.
    Future RFC heading rename silently breaks back-references.
  Proof: `grep -c "RFC-0009 §" MILESTONES.md` returns 3; no automated
    test asserts those anchors resolve.
  Contradiction: at land time anchors resolve; future rename touches
    the author who is expected to grep for back-references.
  Action: deferred (same family as existing FOLLOWUPS rows on docs-
    parity helpers; no new row added)
  Rationale: low-frequency failure mode, manual mitigation sufficient.

P1.4 [NIT] Concurrent FOLLOWUPS.md edit conflict
  Beneficiary: repo-long-term
  Location: docs/FOLLOWUPS.md new section at file tail
  Description: My M13 section sits at end-of-file; concurrent PRs
    appending elsewhere merge cleanly; same-tail concurrent appends
    conflict.
  Proof: PR #77 recently edited FOLLOWUPS.md; my branch was rebased
    onto current main.
  Contradiction: standard git merge handles this; conflict is expected
    workflow, not a defect.
  Action: explicitly-skipped
  Rationale: not a defect.

P1.5 [NIT] fnv128a collision math n=10^7 not workload-cited
  Beneficiary: repo-long-term
  Location: docs/rfcs/0009-pyspy-receiver-scope.md §Design overview
  Description: The (2.7e-6, 1.5e-25) numbers cite the birthday-bound
    formula `n^2 / (2 * 2^k)` but the `n=10^7 distinct (rank, stack)
    pairs per fleet-day` upper bound is asserted without measurement.
  Proof: Python repl: `1e7**2/(2*2**64) = 2.71e-6`;
    `1e7**2/(2*2**128) = 1.47e-25`. Math is correct; n is an estimate.
  Contradiction: reader can re-derive for any n trivially from the
    inline formula. RFC text is falsifiable in shape.
  Action: explicitly-skipped
  Rationale: PRINCIPLES §6 met — formula provided; n is a reasonable
    upper-bound estimate, tightening is polish not correctness.

P1.6 [CONCERN] Non-CPython interpreter support boundary undocumented
  Beneficiary: customer-adopter
  Location: docs/rfcs/0009-pyspy-receiver-scope.md §Degraded modes
  Description: `faulthandler_missing` posture covers CPython-built-
    without-faulthandler but the RFC does not enumerate PyPy /
    MicroPython / GraalPy. An adopter on a non-CPython runtime would
    hit a confusing pip-install failure rather than a clean error.
  Proof: PyPy older versions: `import faulthandler` raises ImportError;
    GraalPy support is divergent across versions.
  Contradiction: ML training is overwhelmingly CPython; non-CPython in
    training is rare; Phase 4 operator docs are the right venue.
  TDD record: deferred — defended by operator docs (Phase 4).
  Action: deferred docs/FOLLOWUPS.md M13 section (this commit)
  Rationale: real constraint, low-frequency, doc-mitigation correct
    venue.

Validation-cycle stats:
- Findings rejected during contradict: 0
- Findings whose hard-proof did not reproduce: 0

TDD discipline stats:
- New code changes landed via failing-test-first: 0 (doc-only PR)
- Tests with mutation-verify outcome recorded: 0
- Tests reproducibility-verified: 0
- doc-check runs in draft cycle: 6 (all clean)

Edge cases enumerated:
- Internal link rot     → defended by doc-check (252 links resolve)
- External link rot     → P1.2 explicitly-skipped
- Anchor brittleness    → P1.3 deferred
- Concurrent edits      → P1.4 explicitly-skipped (standard merge)
- Collision math        → P1.5 explicitly-skipped (formula inline)
- Non-CPython runtime   → P1.6 deferred to FOLLOWUPS
- Rubric drift          → covered by P1.4

Rubric additions proposed in Phase 1: none. Initial rubric (repo-
standards) covers the doc-only diff.

Signed-off-by: Tri Lam <trilamsr@gmail.com>