fix: overlay typewriter RAF idle loop + auto-updater safety

**OverlayPage typewriter infinite RAF loop (MEDIUM)**:
- When typewriter caught up to target text (behind <= 0), it still
  called requestAnimationFrame(tick) every frame, spinning the CPU
  forever doing nothing. Fixed: return without re-scheduling. Added
  `source` to useEffect deps so RAF restarts when new text arrives.

**OverlayPage clipboard empty catch**:
- Clipboard write failure was silently swallowed. Added console.error
  for debuggability.

**Auto-updater safety**:
- Added sendToMain() helper with isDestroyed() check — prevents crash
  if mainWindow is destroyed while updater events fire.
- Initial checkForUpdates catch: now logs error instead of swallowing.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: liangweifeng

electron/auto-updater.ts

@@ -1,6 +1,12 @@
 import { autoUpdater } from 'electron-updater';
 import { state } from './app-state';
 
+/** Safely send to mainWindow — avoids crash if window is destroyed */
+function sendToMain(channel: string, ...args: unknown[]) {
+  const wc = state.mainWindow?.webContents;
+  if (wc && !wc.isDestroyed()) wc.send(channel, ...args);
+}
+
 export function setupAutoUpdater() {
   autoUpdater.autoDownload = false;
   autoUpdater.autoInstallOnAppQuit = true;
@@ -14,31 +20,31 @@ export function setupAutoUpdater() {
     } else if (Array.isArray(info.releaseNotes)) {
       notes = info.releaseNotes.map((n: any) => n.note || n).join('\n');
     }
-    state.mainWindow?.webContents.send('updater:update-available', { version: info.version, releaseNotes: notes });
+    sendToMain('updater:update-available', { version: info.version, releaseNotes: notes });
   });
 
   autoUpdater.on('update-not-available', () => {
     console.log('[Updater] no update available');
-    state.mainWindow?.webContents.send('updater:update-not-available');
+    sendToMain('updater:update-not-available');
   });
 
   autoUpdater.on('download-progress', (progress) => {
-    state.mainWindow?.webContents.send('updater:download-progress', {
+    sendToMain('updater:download-progress', {
       percent: Math.round(progress.percent),
     });
   });
 
   autoUpdater.on('update-downloaded', () => {
     console.log('[Updater] update downloaded');
-    state.mainWindow?.webContents.send('updater:update-downloaded');
+    sendToMain('updater:update-downloaded');
   });
 
   autoUpdater.on('error', (err) => {
     console.error('[Updater] error:', err.message);
-    state.mainWindow?.webContents.send('updater:error', err.message);
+    sendToMain('updater:error', err.message);
   });
 
   setTimeout(() => {
-    autoUpdater.checkForUpdates().catch(() => {});
+    autoUpdater.checkForUpdates().catch((e) => console.error('[Updater] initial check failed:', e.message));
   }, 3000);
 }

src/pages/OverlayPage.tsx

@@ -69,7 +69,7 @@ function useTypewriter(source: string, active: boolean) {
     const tick = (now: number) => {
       const s = stateRef.current;
       const behind = s.target.length - s.pos;
-      if (behind <= 0) { raf = requestAnimationFrame(tick); return; }
+      if (behind <= 0) return; // caught up — RAF restarts via useEffect when source changes
       // Always 1 char at a time; shorten the interval when falling behind
       const interval = behind > 20 ? 10 : behind > 10 ? 18 : behind > 4 ? 25 : 35;
       if (now - s.lastTime >= interval) {
@@ -81,7 +81,7 @@ function useTypewriter(source: string, active: boolean) {
     };
     raf = requestAnimationFrame(tick);
     return () => cancelAnimationFrame(raf);
-  }, [active]);
+  }, [active, source]);
 
   return display;
 }
@@ -174,7 +174,7 @@ export function OverlayPage() {
         setCopied(false);
         window.electronAPI?.hideOverlay();
       }, 1200);
-    } catch {}
+    } catch (e) { console.error('[Overlay] clipboard write failed:', e); }
   }, [rec.processedText]);
 
   const handleDismiss = useCallback(() => window.electronAPI?.hideOverlay(), []);