#23397: fix(memory): raise qmd sqlite busy_timeout for read stability

## What - change QMD SQLite `busy_timeout` from `1ms` to `5000ms` - add a regression test that verifies `PRAGMA busy_timeout = 5000` is applied when opening the index DB ## Why - `busy_timeout=1` is effectively no wait - under normal qmd update writes, read queries can fail with `SQLITE_BUSY` - this makes read-side memory search tolerant to short write lock contention ## Validation - `pnpm check` - `pnpm vitest run src/memory/qmd-manager.test.ts`