[EPIC] docs hardening audit (F2 round)

gh issue create --title "[EPIC] docs hardening audit (F2 round)" --label "epic,audit" --body "## EPIC: docs hardening audit (F2 round)

Source: F2 audit round, 2026-09-03. This EPIC aggregates the 10 findings from the docs audit (3 HIGH, 4 MEDIUM, 3 LOW).

HIGHs include CHANGELOG link-reference drift (resolved-async). MEDIUMs include README and ROADMAP staleness. LOWs include a stray @master reference and a CHANGELOG Unreleased artifact (already fixed).

### HIGH

- [ ] #234 docs H1 — SECURITY.md 'Currently maintained' latest version (CLOSED, fixed by 858de77)
- [ ] #235 docs H2+H3 — CHANGELOG missing link-references for v2.11.0 and v2.11.1; duplicates

### MEDIUM

- [ ] #236 docs M1 — README extended example has broken YAML indentation
- [ ] #237 docs M2 — CHANGELOG v1.3.3 placeholder date 2024-XX-XX
- [ ] #238 docs M3+M4 — ROADMAP stale; inputs count off

### LOW

- [ ] #141 runbook needs updating for protect-main ruleset (existing; F2 added 2 sub-gaps, also in workflows EPIC)
- [ ] #239 docs L2 — README ASCII art mentions @master not @main
- [ ] #240 docs L3 — CHANGELOG Unreleased contained v2.11.2 entry (CLOSED, fixed by PR #170)

## Suggested resolution order

1. Land H2+H3 in v2.11.3 — link-reference cleanup is mechanical and the doc-render bug is user-visible.
2. Batch M1+M2+M3+M4 into a v2.11.4 doc-cleanup release.
3. LOWs into a later cleanup.

## Source

F2 audit 2026-09-03 (docs audit). Reporter: subagent-pekodbj7."

Read child issues #234-240 and the referenced SECURITY.md, CHANGELOG, README, ROADMAP, and runbook first. Treat the epic as an audit checklist: verify which findings remain open, address the documented cleanup, and account for the already closed findings. Done means the remaining checklist items and associated child issues are resolved.

索引モデルが issue の本文から書いたものです。