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/parse-args.test.ts

@@ -127,3 +127,10 @@ test('parseArgs maps stats rebuild action to cleanup lifetime mode', () => {
   assert.equal(parsed.statsCleanupVocab, false);
   assert.equal(parsed.statsCleanupLifetime, true);
 });
+
+test('parseArgs maps doctor refresh-known-words flag', () => {
+  const parsed = parseArgs(['doctor', '--refresh-known-words'], 'subminer', {});
+
+  assert.equal(parsed.doctor, true);
+  assert.equal(parsed.doctorRefreshKnownWords, true);
+});