feat(work): auto-tick epic story bullets when a story finishes

- Add tickStoryBulletInEpic(workRoot, epic, story) helper that finds
  the bullet in the parent epic's `## Stories` section linking to the
  given story folder and flips `- [ ]` to `- [x]`. Idempotent.
- applyApprovedState now ticks the parent epic bullet whenever a
  story flips to status: done (alongside the existing per-task tick
  and epic-status flip). Epic file gets staged on either ticked-or-
  flipped, not just flipped.
- Backfill all 3 existing epics: 21 bullets ticked to match their
  already-done story statuses (binder-wrap-helper x3, library-
  evaluation-policy x9, ci-security-and-supply-chain x9).

docs/work/2026-05-14-library-evaluation-policy/_epic.md

@@ -18,12 +18,12 @@ The repo's narrow third-party surface is uncodified. New dependencies enter via
 
 ## Stories
 
-- [ ] [01 — Trace schema module + docs/library-decisions/ foundation](01-trace-schema-foundation/_story.md)
-- [ ] [02 — Pre-commit check script](02-pre-commit-check-script/_story.md)
-- [ ] [03 — Claude PreToolUse / PostToolUse hooks](03-claude-hooks/_story.md)
-- [ ] [04 — evaluate-library skill](04-evaluate-library-skill/_story.md)
-- [ ] [05 — Human guide: docs/guides/adding-a-library.md](05-human-guide/_story.md)
-- [ ] [06 — Sandcastle reviewer prompt update](06-sandcastle-reviewer-prompt/_story.md)
-- [ ] [07 — Generator pre-shipped traces for optional cores](07-generator-pre-shipped-traces/_story.md)
-- [ ] [08 — Backfill traces for existing runtime deps](08-backfill-traces/_story.md)
-- [ ] [09 — CLAUDE.md Key Conventions bullet](09-claude-md-update/_story.md)
+- [x] [01 — Trace schema module + docs/library-decisions/ foundation](01-trace-schema-foundation/_story.md)
+- [x] [02 — Pre-commit check script](02-pre-commit-check-script/_story.md)
+- [x] [03 — Claude PreToolUse / PostToolUse hooks](03-claude-hooks/_story.md)
+- [x] [04 — evaluate-library skill](04-evaluate-library-skill/_story.md)
+- [x] [05 — Human guide: docs/guides/adding-a-library.md](05-human-guide/_story.md)
+- [x] [06 — Sandcastle reviewer prompt update](06-sandcastle-reviewer-prompt/_story.md)
+- [x] [07 — Generator pre-shipped traces for optional cores](07-generator-pre-shipped-traces/_story.md)
+- [x] [08 — Backfill traces for existing runtime deps](08-backfill-traces/_story.md)
+- [x] [09 — CLAUDE.md Key Conventions bullet](09-claude-md-update/_story.md)