fix: clear stale CSS properties and subtitle state on style/media update

- Remove CSS properties absent from subsequent subtitle style updates
- Broadcast subtitle:set clear when media path changes
- Preserve launcher lifecycle ownership for already-managed overlay apps
- Clamp negative autoplay current time to zero
- Reject blank subminerBinaryPath values via parseNonEmptyString
- Log and rethrow legacy config migration errors instead of swallowing
- Normalize modifier aliases (e.g. CommandOrControl) in keybinding display

launcher/config-domain-parsers.test.ts

@@ -106,6 +106,16 @@ test('parseLauncherMpvConfig reads launch mode preference', () => {
   assert.equal(parsed.aniskipButtonKey, 'F8');
 });
 
+test('parseLauncherMpvConfig ignores blank subminer binary paths', () => {
+  const parsed = parseLauncherMpvConfig({
+    mpv: {
+      subminerBinaryPath: '   ',
+    },
+  });
+
+  assert.equal(parsed.subminerBinaryPath, undefined);
+});
+
 test('parseLauncherMpvConfig ignores invalid launch mode values', () => {
   const parsed = parseLauncherMpvConfig({
     mpv: {