feat(anki): add media timing review before card creation

- Add draggable timing previews with audio playback and exact media ranges
- Support cancellation choices, including deleting existing cards

src/renderer/modals/media-timing-review.test.ts

@@ -0,0 +1,62 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  constrainMediaTimingSelection,
+  createMediaTimingPreviewRequestGuard,
+  formatMediaTimingTimestamp,
+} from './media-timing-review';
+
+test('formatMediaTimingTimestamp renders stable review readouts', () => {
+  assert.equal(formatMediaTimingTimestamp(65.4321), '01:05.432');
+  assert.equal(formatMediaTimingTimestamp(65.4321, false), '01:05');
+  assert.equal(formatMediaTimingTimestamp(-1), '00:00.000');
+  assert.equal(formatMediaTimingTimestamp(119.9999), '02:00.000');
+  assert.equal(formatMediaTimingTimestamp(119.6, false), '02:00');
+});
+
+test('selection constraints preserve the handle that did not move', () => {
+  assert.deepEqual(
+    constrainMediaTimingSelection({
+      nextStart: 3,
+      nextEnd: 2,
+      currentStart: 1,
+      timelineStart: 0,
+      timelineEnd: 10,
+      mediaEnd: 10,
+      maxMediaDuration: 30,
+    }),
+    { start: 1.9, end: 2 },
+  );
+  assert.deepEqual(
+    constrainMediaTimingSelection({
+      nextStart: 1,
+      nextEnd: 0.5,
+      currentStart: 1,
+      timelineStart: 0,
+      timelineEnd: 10,
+      mediaEnd: 10,
+      maxMediaDuration: 30,
+    }),
+    { start: 1, end: 1.1 },
+  );
+});
+
+test('preview request guard blocks overlap and invalidates stale responses', () => {
+  const guard = createMediaTimingPreviewRequestGuard();
+  const first = guard.begin();
+
+  assert.equal(typeof first, 'number');
+  assert.equal(guard.begin(), null);
+  assert.equal(guard.isCurrent(first!), true);
+
+  guard.invalidate();
+  assert.equal(guard.isCurrent(first!), false);
+  assert.equal(guard.isInFlight(), false);
+
+  const second = guard.begin();
+  assert.equal(typeof second, 'number');
+  guard.finish(first!);
+  assert.equal(guard.isCurrent(second!), true);
+  guard.finish(second!);
+  assert.equal(guard.isInFlight(), false);
+});