- Implement scheduler hydration barrier to prevent premature triggers
- Track scheduler exact runs using keys to avoid false stops
- Use 'System Events' for accurate macOS automation permissions
- Prevent system-sleep via proper idle assertions
- Ensure download pauses use channel acknowledgements (PauseWithAck)
- Require Firelink ownership before replacing files in add/conflict UI
- Retain partial download assets when removing entries without deletion
- Clear progress state in store when downloads complete or pause to reduce churn
- Handle empty/invalid queue selections gracefully
This commit replaces the frontend-imperative download dispatcher with a centralized backend `QueueManager`. It acts as the sole concurrency gatekeeper using a single `tokio::sync::Semaphore` across all download paths (aria2 RPC, native HTTP, yt-dlp media).
Backend Changes:
- **queue**: Added `QueueManager` to manage an ordered `VecDeque` of tasks, semaphore permits, and retirement debt (CAS resize).
- **commands**: Replaced direct start commands with `enqueue_download`, `enqueue_many`, `move_in_queue`, and `remove_from_queue`.
- **ipc**: Exported `DownloadStateEvent` and `QueueDirection` to the frontend.
- **tests**: Added 11 integration tests covering idle-parking, idempotent releases, CAS underflow prevention, and gid-completion races.
Frontend Changes:
- **store**: Made `useDownloadStore` reactive to the backend via the `download-state` event.
- **store**: Removed `processQueue` and introduced `pendingOrder` to track the accurate sequence of queued items.
- **ui**: Updated `DownloadItem` with queue visuals (clock icon, position badge).
- **ui**: Added Move Up/Down controls to interact with the backend queue reordering API.
NimBold