Switch known-word cache to incremental sync and doctor refresh

- Load persisted known-word cache on startup; reconcile adds/deletes/edits on timed sync
- Add `knownWords.addMinedWordsImmediately` (default `true`) for immediate mined-word updates
- Route full rebuild to explicit `subminer doctor --refresh-known-words` and expand tests/docs

launcher/types.ts

@@ -119,6 +119,7 @@ export interface Args {
   statsCleanupLifetime?: boolean;
   dictionaryTarget?: string;
   doctor: boolean;
+  doctorRefreshKnownWords: boolean;
   configPath: boolean;
   configShow: boolean;
   mpvIdle: boolean;