fix(scheduler): harden scheduled actions and speed limits

- Persist scheduler dispatch markers and retry unacknowledged events across renderer and process restarts.
- Fence queue admission, Torrent moves, and permit activation during system actions with an explicit force path.
- Preserve Aria2 zero-limit overrides and normalize global limits across startup, queued, retry, and live paths.
- Guard scheduler lifecycle races, completion post-actions, settings bindings, and regression coverage.

src/utils/schedulerCompletion.test.ts

@@ -15,6 +15,10 @@ const download = (id: string, status: DownloadItem['status']): DownloadItem => (
 });
 
 describe('schedulerCompletionState', () => {
+  it('does not treat an empty scheduler set as completed', () => {
+    expect(schedulerCompletionState([], [])).toBe('incomplete');
+  });
+
   it('stays active while any tracked scheduler download can still progress', () => {
     expect(schedulerCompletionState([
       download('a', 'completed'),

src/utils/schedulerCompletion.ts

@@ -7,6 +7,8 @@ export const schedulerCompletionState = (
   downloads: DownloadItem[],
   schedulerActiveDownloadIds: string[],
 ): SchedulerCompletionState => {
+  if (schedulerActiveDownloadIds.length === 0) return 'incomplete';
+
   const scheduledItems = schedulerActiveDownloadIds.map(id =>
     downloads.find(download => download.id === id)
   );

src/utils/schedulerControl.test.ts

@@ -0,0 +1,13 @@
+import { describe, expect, it } from 'vitest';
+import { beginSchedulerControl, isSchedulerControlCurrent } from './schedulerControl';
+
+describe('scheduler control generation', () => {
+  it('invalidates an older asynchronous scheduler operation', () => {
+    const first = beginSchedulerControl();
+    expect(isSchedulerControlCurrent(first)).toBe(true);
+
+    const second = beginSchedulerControl();
+    expect(isSchedulerControlCurrent(first)).toBe(false);
+    expect(isSchedulerControlCurrent(second)).toBe(true);
+  });
+});

src/utils/schedulerControl.ts

@@ -0,0 +1,14 @@
+let schedulerControlGeneration = 0;
+
+/**
+ * Start a new scheduler control lifecycle. A later manual pause or scheduler
+ * event invalidates earlier asynchronous queue operations before they can
+ * publish stale running state.
+ */
+export const beginSchedulerControl = (): number => {
+  schedulerControlGeneration += 1;
+  return schedulerControlGeneration;
+};
+
+export const isSchedulerControlCurrent = (generation: number): boolean =>
+  schedulerControlGeneration === generation;