[thekevinbot]

Fixes #1534

The scanner handles a file-only directory's entries in one pass, with no intermediate list. Frontmatter is about 2-3% faster: 100 alternating pairs of release CLI builds on the same 131,072-note corpus gave a median ratio of 0.971 for this branch against main, and 1.023 for main against this branch.

This is not enough for the fastest-native bar. With the bar set to FASTEST, CI's runner measured 1.132x find+xargs-P before the fix and 1.156x after it, against a 1.1x limit. That difference is noise. Locally the ratio is 1.89x. This PR therefore leaves the frontmatter bar at find+awk and leaves the native assertion out of speed-sanity-ci.yml, which only times against the previous release. The remaining lever, creating the DB and inserting rows during the scan, is L-sized and is tracked in #1560. #1560 also covers switching the bar to FASTEST.

A borrowed-table-name variant of the match step was measured and dropped: 1.064x slower over 100 pairs.

No API change, so there is no parity drift.

E2E Verification

• Ran e2e suites locally for every affected SDK
• Python SDK e2e: pass (on_file_query_test.py, query_contract_test.py, frontmatter_parse_speed_test.py)
• TypeScript SDK e2e: pass (18/18)
• Rust core e2e (if applicable): pass (cargo test --workspace --features cli)
• packages/python/e2e-attestations/<branch>.json receipt written if packages/python changed (just e2e-attest-python)
• packages/ts/e2e-attestations/<branch>.json receipt written if packages/ts changed (just e2e-attest-ts)
• Command(s) run: uv run python -m pytest tests/e2e/on_file_query_test.py tests/e2e/query_contract_test.py tests/e2e/frontmatter_parse_speed_test.py -x -q; pnpm test:e2e; cargo test --workspace --features cli; cargo bench -p dirsql
• Result summary: all pass. Frontmatter is 0.180x find+awk (bar) and 1.887x find+xargs-P (fastest, printed only), load 16.7.

Manual CLI: on 131,072 notes the query returned four status rows of 32,768 notes each, with the expected word sums.

Changelog / Migrations

• Rust changelog fragment under packages/rust/changelog.d/
• Rust migration fragment under packages/rust/migrations.d/