fix: reduce idle CPU usage on macOS (tray title dedup, pause hidden-w…

[Code-newWorld]

…indow polling)

On newer macOS versions (especially with TUN enabled), FlClash keeps a constant 40-50% CPU load in the background. Four independent per-second hot paths cause this:

• Tray.updateTrayTitle called trayManager.setTitle every second even when the value was unchanged or the tray title was disabled. Each setTitle triggers a full NSStatusItem redraw on recent macOS. Now the last title is cached and the native call is skipped when unchanged.
• trayTitleState subscribed to per-second traffic updates even with showTrayTitle off. It now returns a constant state in that case.
• The 1s runtime/traffic poll timer now skips its two core IPC round-trips while the window is hidden and the tray title is off (nothing consumes those values). Resumes automatically on show.
• getTraffic/getTotalTraffic invocations no longer emit two log entries per second each; other methods keep logging as before.
• Request push messages from the core (one per connection under TUN) are no longer JSON-parsed while the window is hidden.

No behavior change while the window is visible.

[Surfire]

I tested the tray-title part of this PR on a real multi-display macOS setup and can confirm the root cause and the effectiveness of the deduplication.

Environment

• macOS 26.5.1
• Apple Silicon
• 3 displays: built-in, 4K external with scaled rendering, and a portrait 1080p display
• "Displays have separate Spaces" enabled
• FlClash 0.8.93
• showTrayTitle=false

Before / after

Official build before the fix:

• FlClash GUI: 36.7%-40.0% CPU while hidden
• 5-second sample: 542 samples under NSStatusItem _updateReplicants

Local build with tray-title deduplication plus the current tray_manager self-drawn-title fix:

• FlClash GUI: 0.0% in 10 consecutive idle samples
• FlClashCore: 0.0%-0.7%
• no _updateReplicants or sizeToFit frames in the installed app's 5-second sample
• proxy remained functional (generate_204 returned 204)

A native harness that changed the tray title every second stayed at 0.1%-0.5% CPU. It had only 3 incidental _updateReplicants samples out of 4,349 main-thread samples and no sizeToFit hot path.

Validation used Flutter 3.41.9: flutter analyze clean, all 353 tests passed, and the macOS Release build succeeded.

Two implementation suggestions

1. Assign _lastTrayTitle = title after await trayManager.setTitle(title). If the platform call fails, assigning before the await suppresses retries for the same title.
2. Reset _lastTrayTitle in destroy(), and add a MethodChannel test covering both deduplication and cache reset.

The title deduplication alone addresses the disabled-title case from #1644. The hidden-window polling and request-parsing changes touch broader behavior, so splitting them from the minimal tray fix may make review and regression analysis easier.

[Code-newWorld]

Thanks for the thorough multi-display validation — really helpful.

I've addressed your implementation notes:

1. _lastTrayTitle is now assigned only after a successful await trayManager.setTitle(title), so a failed platform call can retry the same title.
2. destroy() already resets _lastTrayTitle; I added MethodChannel tests covering deduplication, cache reset after destroy, and the failed-setTitle retry path.

Agreed on splitting. I've opened a minimal tray-title-only PR here: #2201

The hidden-window polling / request-parsing / silent-IPC changes can follow in a separate PR.