refactor(recall): remove auto-recall PostToolUse hook in favor of teamai-recall subagent

[hsuchifeng]

Summary

• Removes the auto-recall PostToolUse hook that silently fired on every Bash/Grep/WebSearch/WebFetch tool call to search the team knowledge base. In practice it was noisy and low-hit-rate, and is now superseded by the teamai-recall subagent (proactive, codebase-graph aware, structured summary output) plus the manual teamai recall command.
• Installed machines self-clean the stale hook entries on the next teamai pull / hooks inject via the existing reconcile engine — no manual migration needed.
• contribute-check's Phase 2 knowledge-gap detection depended on auto-recall's quality cache (~/.teamai/sessions/<sid>-recall-cache.json). That cache is now written by teamai recall itself (extracted into a standalone src/recall-quality.ts module), so the feature keeps working with an equivalent-but-more-accurate data source — both manual recall and the subagent's underlying teamai recall call now populate it.
• TEAMAI_RECALL_DISABLED=1 now gates teamai recall's quality tracking instead of the removed hook.

Test plan

• npx tsc --noEmit
• npm run build (tsup)
• npx vitest run — 1569 passed, 3 pre-existing failures in import-repo-merge.test.ts unrelated to this change (present on main before this branch)
• Added src/__tests__/recall-quality.test.ts covering recordRecallQuality/readRecallQuality
• Added quality-tracking coverage in recall-scope-isolation.test.ts (hit + miss cases)
• Updated golden hook fixtures (claude/claude-internal/codebuddy/cursor) and all hook-count assertions across hooks*.test.ts
• contribute-check-phase2.test.ts passes unchanged (cache format untouched)

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