docs(patterns): backfill #14 walkthrough + document #6/#15 gaps

[trilamsr]

Summary

Closes the missing-pattern-docs gap in docs/patterns/ for the two
numerically-missing IDs (#6, #14) against NORTHSTARS Appendix A's
15-pattern roster.

Investigation

Surveyed module/pkg/patterns/, NORTHSTARS Appendix A, and
MILESTONES M18/M19 to pin actual detector state per ID:

ID	NORTHSTARS Appendix A claim	Actual repo state	Decision
#6 Stragglers (M18)	☑ in-tree detector	No detector exists — no straggler*.go, no data_time aggregation, no replay fixture. Only failure-inject cpu-steal chaos hook (M4b) lands the symptom. MILESTONES line 237 acknowledges M18 is at-risk and build-time-coupled to M17's cross_rank.go. The Appendix A mark is aspirational, not current state.	Option B — README gap-note explicitly documenting the unimplemented state + linking the M18 milestone. Reconciliation of Appendix A's claim is left for the detector-shipping PR.
#14 Pod evicted (M19)	☑ in-tree detector	Shipped — patterns.PodEvictedDetector in module/pkg/patterns/pod_evicted.go, processor wiring in module/processor/patterndetectorprocessor/, canonical replay fixture at module/pkg/replay/pod_evicted/canonical/.	Option A — backfill full operator walkthrough 14-pod-evicted-walkthrough.md following the 02-ib-link-flap-walkthrough.md template (Symptom → Signal → Query → Alert → Escalation → Replay → Detector status → Verdict shape → Integration recipe).

Also surfaced #15 (Image pull / FailedMount on restart) — present
in Appendix A but absent from this directory. Added to the same
"Reserved / unfilled" table for completeness so every Appendix A
ID is accounted for somewhere in docs/patterns/.

Changes

• docs/patterns/14-pod-evicted-walkthrough.md (new, ~210 lines) —
  full operator walkthrough sourced from
  module/pkg/patterns/pod_evicted.go godoc, verdict.go
PodEvictedVerdict struct, processor config knobs
  (join_window, emit_partial_verdicts), the
  k8sobjectsreceiver integration recipe, and the canonical replay
  fixture's headline regex contract.
• docs/patterns/README.md — adds the [docs] FOLLOWUPS: close squash-merge-trailer item with observation #14 row to the Operator
  walkthroughs (shipped) table; rewrites the coverage prose
  (5 → 7 patterns walkthrough'd); adds a new "Reserved / unfilled"
  section documenting Make RFC process optional, not gated #6 and [telemetry] Add SelfTelemetry interface + agent infra scaffolding #15 explicitly so the numeric gaps in
  the existing tables are no longer silent.

Test plan

• make doc-check green — all markdown links + anchors resolve,
  banned-phrase lint clean, walkthrough renders.
• Pre-commit hooks pass (golangci-lint, go vet,
  go mod verify, attribute-namespace-check,
  deprecation-check).
• Cross-checked every link in the new walkthrough resolves to a
  real on-disk file (pod_evicted.go, pod_evicted_test.go,
  pod_evicted_bench_test.go, replay/pod_evicted/canonical/,
  k8sobjects-events.md, ATTRIBUTES.md,
  example_config.yaml).

docs(patterns): add operator walkthrough for pattern #14 (pod evicted); document pattern #6 + #15 gaps in the patterns README.

[trilamsr]

Adversarial review (independent pass): grade A.

Findings:

1. (ACT, fixed in 7fd2022) — alert YAML filtered on k8s.namespace.name, which is not in the customer-stable scalar-promotion contract (verdict.go:60-62 only promotes k8s.pod.namespace). Operators following the walkthrough would write a filter that silently matches nothing once the verdict-driven dashboard ships. Swapped to k8s.pod.namespace.
2. (DROP) — count_over_time({...}) is LogQL-flavored, but the section header already labels it 'OTLP filter — post-OTTL' (log records, not metrics), so the syntax flavor is honest.
3. (verified) — every pattern.* and k8s.* verdict attribute in the walkthrough's verdict-shape table matches the constants in module/processor/patterndetectorprocessor/patterndetector.go:115-127 and module/pkg/patterns/verdict.go:59-77.
4. (verified) — headline regex /Pod .* evicted at .* due to .* pressure/ matches the canonical fixture's golden.json headline.
5. (verified) — Make RFC process optional, not gated #6 gap-note is accurate: no straggler*.go, no data_time aggregator in module/pkg/patterns/; NORTHSTARS Appendix A's ☑ in-tree detector mark is aspirational.
6. (verified) — coverage count 'Seven of 15' = ci(deps): bump the gh-actions group with 5 updates #1, Bump the gh-actions group across 1 directory with 4 updates #2, Add NORTHSTARS, RFC-0002, and Q1 MILESTONES #3, Wave 1: governance bootstrap (CODEOWNERS, DCO, signing) #4, Apply Wave-1 follow-ups: tests, automation, doc-truth #5, Add AI review + PR-creation gates and lifecycle skills #7, [docs] FOLLOWUPS: close squash-merge-trailer item with observation #14 in the shipped table.
7. (verified) — every referenced file path exists on disk: example_config.yaml, pod_evicted_test.go, pod_evicted_bench_test.go, replay/pod_evicted/canonical/, replay/pod_evicted/_negative/, replay/pod_evicted/_real_world/, k8sobjects-events.md, ATTRIBUTES.md.

Grade A: doc-only PR with one load-bearing fix applied. Auto-merge armed.