docs: reconcile 3 stale doc references post-v0.2.0 (closes #256 #257 #259)

[trilamsr]

Summary

Three concern-isolated doc-rot reconciles, one commit per issue:

• pyspy README: stale 2026-05-22 deletion banner — pyspy stays in v0.3.0 per #222 #256 — components/receivers/pyspy/README.md + RUNBOOK.md reframe the stale 2026-05-22 "Scheduled for deletion at v0.3.0" banner to "deferred to v0.4.0+ per #222" with the OTel-Profiles-→-Beta + parca-agent-OTLP-export re-evaluation triggers named verbatim.
• RFC-0013 §Migration: stale PR-M/PR-N v0.3.0 sequencing — deferred to v0.4.0+ per #222 #257 — docs/rfcs/0013-distro-first-pivot.md adds deferral banners at §4 Migration timeline (v0.3.0 row) and §Migration/rollout v0.3.0 sequencing; annotates the §7 Deletion list rows + PR-M sequencing entry with explicit (deferred to v0.4.0+ per #222) markers. Historical sequencing preserved verbatim (option 1 from the issue).
• docs: reconcile reproducibility.md with goreleaser removal (#258) #259 — docs/reproducibility.md + docs/notes/reproducibility.md reconciled against post-PR-fix(release): replace goreleaser pro-only prebuilt builder with OSS-compatible shape #258 inline-shell package job: drop all .goreleaser.yaml / .goreleaser.yml / goreleaser.yml signer-workflow references; reframe build narrative around SOURCE_DATE_EPOCH + tar --mtime + --sort=name + gzip -n deterministic-byte controls; update download patterns + verification commands to operate on tar.gz archives; add an explicit sha256sum -c checksums.txt step so the operator integrity chain (sha256sum → checksums.txt → cosign bundle) is named in the walkthrough. Cosign bundle naming unchanged.

Root causes

• pyspy README: stale 2026-05-22 deletion banner — pyspy stays in v0.3.0 per #222 #256: banner predates the PR-M deferral memo in PR-M: parca-agent recipe + delete pyspy — DEFERRED to v0.4.0+ #222; PR docs(migration): reconcile v0.2-to-v0.3 with PR-M v0.4.0+ deferral #254 reconciled docs/migration/v0.2-to-v0.3.md but explicitly left the receiver READMEs out of scope.
• RFC-0013 §Migration: stale PR-M/PR-N v0.3.0 sequencing — deferred to v0.4.0+ per #222 #257: PR docs(migration): reconcile v0.2-to-v0.3 with PR-M v0.4.0+ deferral #254's References section flagged the RFC body with a "supersede with PR-M: parca-agent recipe + delete pyspy — DEFERRED to v0.4.0+ #222" note but the body itself was untouched.
• docs: reconcile reproducibility.md with goreleaser removal (#258) #259: PR fix(release): replace goreleaser pro-only prebuilt builder with OSS-compatible shape #258 (goreleaser → inline shell) deletes .goreleaser.yaml; the reproducibility docs additionally referenced a never-existed .github/workflows/goreleaser.yml signer-workflow path (the file has always been release.yml), so the docs were doubly-broken pre-fix(release): replace goreleaser pro-only prebuilt builder with OSS-compatible shape #258 and singly-broken post-fix(release): replace goreleaser pro-only prebuilt builder with OSS-compatible shape #258.

Sequencing note

PR #258 is the source of truth for the post-pivot inline-shell package job referenced by the #259 reconcile. #258 is currently open + green; if #258 merges first, the doc paths are immediately accurate. If this PR merges first, the docs describe the target state and converge once #258 lands. Either order works.

Test plan

• bash scripts/doc-check.sh — clean (500 markdown links resolve, 47 non-.md intra-repo links resolve, banned-phrase lint clean, all required sections present, 10 fenced bash/sh blocks in docs/reproducibility.md shell-syntax-clean).
• make check — clean (gofumpt, tidy-check, golangci-lint 0 issues, go vet, go mod verify).
• Manual cross-link spot check: confirmed the new #222 issue links + docs/migration/v0.2-to-v0.3.md cross-references resolve; confirmed RFC (deferred to v0.4.0+ per #222) markers attached at every flagged line (matrix row, deletion-list rows, §Migration/rollout sequencing entry); confirmed reproducibility docs no longer mention goreleaser anywhere via grep -i goreleaser.
• Verified no in-flight conflicts with PR docs(migration): reconcile v0.2-to-v0.3 with PR-M v0.4.0+ deferral #254 (already-merged migration-guide reconcile) or PR fix(release): replace goreleaser pro-only prebuilt builder with OSS-compatible shape #258 (still-open inline-shell pivot — touches .github/workflows/release.yml + deletes .goreleaser.yaml, no overlap with this PR's files).

Out of scope / follow-ups

No new doc-rot noticed beyond the three issues addressed here.

docs: reconcile three stale references post-v0.2.0: pyspy README + RUNBOOK + RFC-0013 §Migration now correctly reflect that PR-M (parca-agent recipe + pyspy delete) is deferred to v0.4.0+ pending OTel Profiles → Beta + parca-agent OTLP export (#222); reproducibility docs (docs/reproducibility.md + docs/notes/reproducibility.md) updated for the post-#258 inline-shell `package` job — operator-facing integrity chain (sha256sum → checksums.txt → cosign bundle → SLSA attestation) preserved end-to-end.

Closes #256.
Closes #257.
Closes #259.