test: add mirror-watcher and redis tests (18 tests)

mirror-watcher.test.ts: MirrorWriteTracker (own write detection,
consume, edge cases) + scanMirrorDirs (note/task import, empty dir,
skip non-dirs, skip dirs without events) — 10 tests

redis.test.ts: REDIS_DEFAULTS values, parseRedisTtl for seconds,
minutes, hours, days, combined durations — 8 tests

1915 tests across 54 suites.

Author: prih