The fileuploader.log rotation introduced in 3.3.2 lived inline in
main.js — fine for the runtime path, but it required electron's `app`
to even reach the function under test. Pull the rotation logic into
lib/log-rotation.js (pure fs/path, no electron deps) and cover it
properly:
- ENOENT (file missing) → no-op
- Below cap → no-op
- Over cap → live → .1, returns true
- Existing backups shift up: .1 → .2, .2 → .3
- At maxBackups limit → oldest dropped, others shift, live becomes .1
- Idempotent: rotating twice keeps the chain consistent
- maxBackups=1: never grows past .1
- Invalid maxBytes (0/negative/NaN) → safe no-op
- Provided debug callback receives a "rotated" message
- File without extension still rotates correctly
main.js now imports `maybeRotateLogFile` and calls it directly. 97/97
tests pass.
