* test(lbug): stabilize rel-csv-split Windows CI with expect.poll
Fixed sleeps assumed readline had already created the first mock stream
within 20ms; windows-latest can lag, causing streams.length===0 and
ENOTEMPTY tempdir cleanup. Poll up to 10s instead (Vitest 4).
Refs #1051
Made-with: Cursor
* test(lbug): use exact toBe assertions in rel-csv-split (DoD §2.7)
- Poll for streams.length === 2 after unblock (two pair keys only)
- disk-full test: streams.length === 1 for single Function|Class row
Made-with: Cursor
* test(lbug): replace rel-csv-split setTimeout waits with expect.poll
Shared pollOpts; drain-listener and disk-full tests now wait on streams.length
instead of fixed 50ms sleeps (DoD §2.7 deterministic tests).
Made-with: Cursor