test(db-base): cover withRetry, corruption predicate, and cleanup helpers

[sebastianbreguel]

Why

src/db-base.ts (493L) carries the SQLite primitives behind several recent incident fixes — withRetry (#263 wrapped indexPlainText/indexJSON/searchTrigram, #243 concurrent inserts), isSQLiteCorruptionError + renameCorruptDB (recovery path for #244 heavy-load death and #218 multi-session contention), and the WAL/cleanup helpers touched by #103 lifecycle guard and #249 marketplace-install fallout. Until now the module was only exercised indirectly via SessionDB integration tests.

This PR is pure regression-guard coverage for the pure, framework-free utilities. No changes to src/.

What's covered

withRetry (11 tests) — first-try success, retry-on-busy (Error), retry on "database is locked" string shape (bun:sqlite), rethrow of non-busy errors, rethrow of generic errors, non-Error throws (string, busy-shaped vs not), exhaustion with descriptive after N retries message, attempts = delays.length + 1 invariant, empty-delays short-circuit, and actual wall-clock delay verification (50ms lower bound).

isSQLiteCorruptionError (6 tests) — all four documented signatures (SQLITE_CORRUPT, SQLITE_NOTADB, database disk image is malformed, file is not a database), embedded in longer stack traces, and negative cases (SQLITE_BUSY, ENOENT, empty string).

renameCorruptDB (4 tests) — main-file quarantine with .corrupt-<ts> suffix, sidecar -wal/-shm rename when present, graceful no-op when sidecars or main file are missing.

cleanOrphanedWALFiles (3 tests) — sidecars removed only when the main DB is gone, sidecars preserved when DB still exists, tolerates empty dirs.

deleteDBFiles (3 tests) — unconditional removal of all three files, tolerant of partial/full absence.

defaultDBPath (4 tests) — pid embedding, custom prefix, default prefix, tmpdir scoping.

Test plan

• npx vitest run tests/db-base.test.ts → 31/31 green, 66ms
• Full suite on this branch vs clean next: same pre-existing 5 flakes in tests/hooks/integration.test.ts (SyntaxError: Unexpected end of JSON input from subprocess stdout) — not introduced here.
• No imports or exports in src/ changed.

Single-concern PR; no runtime changes, no perf claims.

[mksglu]

Hi @sebastianbreguel Nice work. Can you please continue that with exist test files instead of create a new one.

[sebastianbreguel]

Hi @mksglu, thanks for the feedback! Done — moved all 31 db-base tests into the existing tests/session/session-db.test.ts (SessionDB extends these primitives, so they live together now) and deleted the separate tests/db-base.test.ts. File goes from 609 → 893 lines. Full suite still green: 28 SessionDB + 31 db-base = 59/59 passing locally. Ready for another look.