Improve startup dictionary sync UX and default playback keybindings

- Add default `f` fullscreen overlay binding and switch default AniSkip skip key to `Tab`
- Make character-dictionary auto-sync non-blocking at startup with tokenization gating for Yomitan mutations
- Add ordered startup OSD progress (checking/generating/updating/importing), refresh current subtitle on sync completion, and extend regression tests

src/main/runtime/startup-osd-sequencer.test.ts

@@ -0,0 +1,134 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  createStartupOsdSequencer,
+  type StartupOsdSequencerCharacterDictionaryEvent,
+} from './startup-osd-sequencer';
+
+function makeDictionaryEvent(
+  phase: StartupOsdSequencerCharacterDictionaryEvent['phase'],
+  message: string,
+): StartupOsdSequencerCharacterDictionaryEvent {
+  return {
+    phase,
+    message,
+  };
+}
+
+test('startup OSD keeps dictionary progress hidden until tokenization and annotation loading finish', () => {
+  const osdMessages: string[] = [];
+  const sequencer = createStartupOsdSequencer({
+    showOsd: (message) => {
+      osdMessages.push(message);
+    },
+  });
+
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('syncing', 'Updating character dictionary for Frieren...'),
+  );
+  sequencer.showAnnotationLoading('Loading subtitle annotations |');
+  sequencer.markTokenizationReady();
+
+  assert.deepEqual(osdMessages, ['Loading subtitle annotations |']);
+
+  sequencer.showAnnotationLoading('Loading subtitle annotations /');
+  assert.deepEqual(osdMessages, [
+    'Loading subtitle annotations |',
+    'Loading subtitle annotations /',
+  ]);
+
+  sequencer.markAnnotationLoadingComplete('Subtitle annotations loaded');
+  assert.deepEqual(osdMessages, [
+    'Loading subtitle annotations |',
+    'Loading subtitle annotations /',
+    'Updating character dictionary for Frieren...',
+  ]);
+});
+
+test('startup OSD buffers checking behind annotations and replaces it with later generating progress', () => {
+  const osdMessages: string[] = [];
+  const sequencer = createStartupOsdSequencer({
+    showOsd: (message) => {
+      osdMessages.push(message);
+    },
+  });
+
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('checking', 'Checking character dictionary for Frieren...'),
+  );
+  sequencer.showAnnotationLoading('Loading subtitle annotations |');
+  sequencer.markTokenizationReady();
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('generating', 'Generating character dictionary for Frieren...'),
+  );
+
+  assert.deepEqual(osdMessages, ['Loading subtitle annotations |']);
+
+  sequencer.markAnnotationLoadingComplete('Subtitle annotations loaded');
+
+  assert.deepEqual(osdMessages, [
+    'Loading subtitle annotations |',
+    'Generating character dictionary for Frieren...',
+  ]);
+});
+
+test('startup OSD skips buffered dictionary ready messages when progress completed before it became visible', () => {
+  const osdMessages: string[] = [];
+  const sequencer = createStartupOsdSequencer({
+    showOsd: (message) => {
+      osdMessages.push(message);
+    },
+  });
+
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('syncing', 'Updating character dictionary for Frieren...'),
+  );
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('ready', 'Character dictionary ready for Frieren'),
+  );
+  sequencer.markTokenizationReady();
+  sequencer.markAnnotationLoadingComplete('Subtitle annotations loaded');
+
+  assert.deepEqual(osdMessages, ['Subtitle annotations loaded']);
+});
+
+test('startup OSD shows dictionary failure after annotation loading completes', () => {
+  const osdMessages: string[] = [];
+  const sequencer = createStartupOsdSequencer({
+    showOsd: (message) => {
+      osdMessages.push(message);
+    },
+  });
+
+  sequencer.showAnnotationLoading('Loading subtitle annotations |');
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('failed', 'Character dictionary sync failed for Frieren: boom'),
+  );
+  sequencer.markTokenizationReady();
+  sequencer.markAnnotationLoadingComplete('Subtitle annotations loaded');
+
+  assert.deepEqual(osdMessages, [
+    'Loading subtitle annotations |',
+    'Character dictionary sync failed for Frieren: boom',
+  ]);
+});
+
+test('startup OSD reset requires the next media to wait for tokenization again', () => {
+  const osdMessages: string[] = [];
+  const sequencer = createStartupOsdSequencer({
+    showOsd: (message) => {
+      osdMessages.push(message);
+    },
+  });
+
+  sequencer.markTokenizationReady();
+  sequencer.reset();
+  sequencer.notifyCharacterDictionaryStatus(
+    makeDictionaryEvent('syncing', 'Updating character dictionary for Frieren...'),
+  );
+
+  assert.deepEqual(osdMessages, []);
+
+  sequencer.markTokenizationReady();
+  assert.deepEqual(osdMessages, ['Updating character dictionary for Frieren...']);
+});