feat(overlay): add optional subtitle selection modal

- Add primary and secondary mpv track selection from the overlay
- Support configurable sequence shortcuts with conflict detection and hot reload
- Document settings, shortcuts, and generated config defaults

src/config/resolve/subtitle-selection.test.ts

@@ -0,0 +1,63 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { resolveConfig } from '../resolve';
+import { DEFAULT_CONFIG } from '../definitions';
+import { buildConfigSettingsRegistry } from '../settings/registry';
+import { resolveConfiguredShortcuts } from '../../core/utils/shortcut-config';
+import {
+  compileSessionBindings,
+  buildPluginSessionBindingsArtifact,
+} from '../../core/services/session-bindings';
+
+function bindings(config: ReturnType<typeof resolveConfig>['resolved']) {
+  return compileSessionBindings({
+    shortcuts: resolveConfiguredShortcuts(config, DEFAULT_CONFIG),
+    keybindings: config.keybindings,
+    platform: 'linux',
+  });
+}
+
+test('subtitle selection is opt-in and enabling it compiles g-s for mpv and the overlay', () => {
+  const defaults = resolveConfig({}).resolved;
+  assert.equal(defaults.subtitleSelection.enabled, false);
+  assert.equal(defaults.shortcuts.openSubtitleSelection, 'g-s');
+  const find = (config: typeof defaults) =>
+    bindings(config).bindings.find(
+      (binding) =>
+        binding.actionType === 'session-action' && binding.actionId === 'openSubtitleSelection',
+    );
+  assert.equal(find(defaults), undefined);
+  const enabled = resolveConfig({ subtitleSelection: { enabled: true } }).resolved;
+  const binding = find(enabled);
+  assert.ok(binding);
+  assert.deepEqual(binding.key, { code: 'KeyG-KeyS', modifiers: [] });
+  assert.equal(bindings(enabled).warnings.length, 0);
+  const artifact = buildPluginSessionBindingsArtifact({
+    bindings: [binding],
+    warnings: [],
+    numericSelectionTimeoutMs: 1000,
+  });
+  assert.deepEqual(artifact.bindings[0], {
+    ...binding,
+    cliArgs: ['--session-action', '{"actionId":"openSubtitleSelection"}'],
+  });
+  enabled.subtitleSelection.enabled = false;
+  assert.equal(find(enabled), undefined);
+});
+
+test('subtitle selection settings are validated, hot reloadable, and the shortcut can be cleared', () => {
+  // @ts-expect-error Config files can contain invalid values at runtime.
+  const { resolved, warnings } = resolveConfig({ subtitleSelection: { enabled: 'yes' } });
+  assert.equal(resolved.subtitleSelection.enabled, false);
+  assert.equal(warnings.length, 1);
+  const field = buildConfigSettingsRegistry(resolved).find(
+    (entry) => entry.configPath === 'subtitleSelection.enabled',
+  );
+  assert.equal(field?.category, 'behavior');
+  assert.equal(field?.restartBehavior, 'hot-reload');
+  const cleared = resolveConfig({
+    subtitleSelection: { enabled: true },
+    shortcuts: { openSubtitleSelection: null },
+  }).resolved;
+  assert.equal(resolveConfiguredShortcuts(cleared, DEFAULT_CONFIG).openSubtitleSelection, null);
+});