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/main.test.ts

@@ -178,6 +178,33 @@ test('doctor reports checks and exits non-zero without hard dependencies', () =>
   });
 });
 
+test('doctor refresh-known-words forwards app refresh command without requiring mpv', () => {
+  withTempDir((root) => {
+    const homeDir = path.join(root, 'home');
+    const xdgConfigHome = path.join(root, 'xdg');
+    const appPath = path.join(root, 'fake-subminer.sh');
+    const capturePath = path.join(root, 'captured-args.txt');
+    fs.writeFileSync(
+      appPath,
+      '#!/bin/sh\nif [ -n "$SUBMINER_TEST_CAPTURE" ]; then printf "%s\\n" "$@" > "$SUBMINER_TEST_CAPTURE"; fi\nexit 0\n',
+    );
+    fs.chmodSync(appPath, 0o755);
+
+    const env = {
+      ...makeTestEnv(homeDir, xdgConfigHome),
+      PATH: '',
+      Path: '',
+      SUBMINER_APPIMAGE_PATH: appPath,
+      SUBMINER_TEST_CAPTURE: capturePath,
+    };
+    const result = runLauncher(['doctor', '--refresh-known-words'], env);
+
+    assert.equal(result.status, 0);
+    assert.equal(fs.readFileSync(capturePath, 'utf8'), '--refresh-known-words\n');
+    assert.match(result.stdout, /\[doctor\] mpv: missing/);
+  });
+});
+
 test('youtube command rejects removed --mode option', () => {
   withTempDir((root) => {
     const homeDir = path.join(root, 'home');