Add read-only external Yomitan profile support

- add `yomitan.externalProfilePath` config and default/template wiring
- load Yomitan from an external Electron profile/session when configured
- disable SubMiner Yomitan writes/settings UI in external-profile mode and update docs/tests

src/config/definitions/domain-registry.test.ts

@@ -27,6 +27,7 @@ test('config option registry includes critical paths and has unique entries', ()
     'ankiConnect.enabled',
     'anilist.characterDictionary.enabled',
     'anilist.characterDictionary.collapsibleSections.description',
+    'yomitan.externalProfilePath',
     'immersionTracking.enabled',
   ]) {
     assert.ok(paths.includes(requiredPath), `missing config path: ${requiredPath}`);
@@ -44,6 +45,7 @@ test('config template sections include expected domains and unique keys', () =>
     'startupWarmups',
     'subtitleStyle',
     'ankiConnect',
+    'yomitan',
     'immersionTracking',
   ];