test: add unit tests (41) and UI smoke tests (21), fix semaphore listener leak
- 12 Semaphore tests: FIFO ordering, abort support, limit updates, listener cleanup
- 8 Throttle tests: rate limiting, abort signal, concurrent consume, updateRate
- 9 ConfigStore tests: defaults, merge, round-trip, corruption fallback, history cap
- 12 UploadManager tests: progress events, retry, cancel, size filter, concurrency
- 21 UI smoke tests: tab navigation, settings panels, statusbar, context menu
- Fix: Semaphore.release() and updateLimit() now properly remove abort listeners
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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