fix: harden account rotation and active download recovery

Apply account enablement changes optimistically and persist rapid toggles sequentially without losing clicks.

Refresh Mega-Debrid API and Web account pools during active downloads, isolate per-account cancellation budgets, rotate within the same conversion attempt, and keep pause, stop, resume, reset, and no-account gates consistent.

Use the native Electron clipboard under Remote Desktop and make support bundle export bounded, redacted, responsive, guarded, visible, and atomic.

Add end-to-end regressions for live account switching, persisted partial recovery, support export, native copy, availability preservation, and the 500 ms telemetry cadence.

tests/visual/mock-electron-api.ts

@@ -139,6 +139,7 @@ export function createVisualElectronApi(
       fixture.snapshot.settings.clipboardWatch = fixture.snapshot.clipboardActive;
       return fixture.snapshot.clipboardActive;
     },
+    writeClipboardText: async () => true,
     pickFolder: async () => "C:\\Visual\\Selected",
     pickContainers: async () => ["C:\\Visual\\Containers\\visual.dlc"],
     getSessionStats: async () => ({