feat(dictionary): add Hachidori backend support

- Add backend selection, setup gating, Anki integration, and external host support
- Add launcher flags, documentation, packaging, and focused tests
- Open on-demand overlay modals on the first attempt

src/config/definitions/defaults-core.ts

@@ -2,6 +2,7 @@ import { ResolvedConfig } from '../../types/config';
 
 export const CORE_DEFAULT_CONFIG: Pick<
   ResolvedConfig,
+  | 'dictionaryBackend'
   | 'subtitlePosition'
   | 'keybindings'
   | 'websocket'
@@ -18,6 +19,7 @@ export const CORE_DEFAULT_CONFIG: Pick<
   | 'notifications'
   | 'auto_start_overlay'
 > = {
+  dictionaryBackend: 'yomitan',
   subtitlePosition: { yPercent: 10 },
   keybindings: [],
   websocket: {

src/config/definitions/options-core.ts

@@ -81,6 +81,13 @@ export function buildCoreConfigOptionRegistry(
   ] as const;
 
   return [
+    {
+      path: 'dictionaryBackend',
+      kind: 'enum',
+      enumValues: ['yomitan', 'hachidori'],
+      defaultValue: defaultConfig.dictionaryBackend,
+      description: 'Dictionary lookup backend. Restart SubMiner after changing this setting.',
+    },
     {
       path: 'logging.level',
       kind: 'enum',

src/config/definitions/template-sections.ts

@@ -1,6 +1,14 @@
 import { ConfigTemplateSection } from './shared';
 
 const CORE_TEMPLATE_SECTIONS: ConfigTemplateSection[] = [
+  {
+    title: 'Dictionary Backend',
+    description: ['Select the dictionary lookup backend: yomitan or hachidori.'],
+    notes: [
+      'Restart SubMiner after changing the backend. Each backend keeps separate settings and dictionaries.',
+    ],
+    key: 'dictionaryBackend',
+  },
   {
     title: 'Japanese Subtitle Generation',
     description: [