fix(scope): close remaining #85 scope-isolation gaps

[jeff-r2026]

Summary

#73/#77 fixed recall's dual-scope merge and #91 fixed auto-recall's upvote scope, but #85 flagged four more places where project vs user scope still leaked into each other. This closes the remaining gaps:

• hooks-cmd.ts: hooks inject/hooks remove reconciled the user-home copy of team hooks using the project's manifest instead of the user's own, diverging from pull.ts's per-scope reconcile and risking duplicate injection / wrongful cleanup of shared tool settings files (e.g. ~/.cursor/hooks.json).
• tags.ts: subscribe/unsubscribe/list/add/remove always read and wrote ~/.teamai/config.yaml, ignoring project-scope installs entirely.
• contribute.ts: wrote new learnings to the team repo but never rebuilt the local search index, so recall couldn't see a fresh contribution until the next pull.
• types.ts / config.ts: getTeamaiHome()/resolveBaseDir() silently fell back to the user home directory when a project LocalConfig was missing projectRoot (e.g. a pre-migration config.yaml). Now detectProjectConfig()/loadLocalConfigForScope() backfill projectRoot from the directory the config was actually loaded from, and the scope helpers throw instead of silently degrading if it's ever still missing.

Closes #85

Test plan

• npx tsc --noEmit — zero errors
• npx vitest run — 130 files / 1686 tests passed
• New e2e suite (scope-isolation-e2e-issue85.test.ts) drives the built CLI against real git fixtures, covering all four fixes: hooks manifest scoping + inject idempotency + remove cleanup, tags scope isolation, contribute→recall immediacy, and the projectRoot backfill
• Strengthened hooks-cmd.test.ts to assert the project/user manifest paths are distinct and correctly scoped
• Updated the two scope.test.ts cases that previously asserted the old silent-fallback behavior to assert the new throw instead

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