test/shards.test.ts runs in under 1 s again: it took 0.3 s on 2026-10-21 and 10.4 s on main today #8310

scripts/test-times.json (recorded 2026-10-21) gives test/shards.test.ts 0.3 s. On main at 48bffd32 it runs 82 tests in 10.4 s alone. Other files on the same machine ran within 1.0–1.3× their recording (apps.test.ts 10.9 → 11.0 s, migrate.test.ts 5.9 → 7.7 s), so this is a 34× regression in the file, not in the machine.

Done when:

• [ ] The pull names what made it slow: a test that shells out, walks the tree, imports scripts/gate.ts per test, or something else
• [ ] The file runs under 1 s alone, every test under 100 ms, and what each test proves is unchanged
• [ ] scripts/test-times.json's entry for it is re-recorded

Files: test/shards.test.ts, scripts/test-shards.ts (only if the cost is there) Risk: do not weaken an assertion. If one was wrong, say which.