chunking: consolidated deferred findings from PR #55 review

[edheltzel]

Source: PR #55 review — six non-blocking findings deferred at merge, consolidated here per the review's request (full detail in the PR #55 review comments).

Highlights:

1. Guard test for the chunk.ts audit note — the audit claim ("only input-scaled SQL path") can rot silently; a test or lint sweep should fail when a new input-scaled IN (...) bypasses chunked().
2. hooks/ carve-out clause — the helper's "must chunk through this helper" prescription is unreachable from hooks/ (self-contained rule); the audit note needs an explicit carve-out + the hooks-side convention documented.
3. Remaining minor items as listed in the PR feat(db): add shared SQLite-safe chunking for input-scaled bind lists #55 review thread (embeddings-orphan item was folded into repair Add mem repair for data and index maintenance #46, since shipped).