feat: continue Priority 2 fixes - non-null assertions and return types

🚀 Priority 2 Progress:
- Fixed missing return types in test-apps/electron-test/src/index.ts (1 function)
- Fixed non-null assertions in examples/hello-poll.ts (2 assertions)
- Enhanced type safety with proper null checks instead of assertions
- Reduced non-null assertions from 26 to 24

Console statements: 0 remaining (100% complete)
Return types: 9 remaining (down from 62, 85% reduction)
Non-null assertions: 24 remaining (down from 26, 8% reduction)

Linting status: ✅ 0 errors, 60 warnings (down from 436 warnings)
Total improvement: 376 warnings fixed (86% reduction)
Priority 2: Excellent progress - approaching completion!

Timestamp: Tue Oct 7 09:52:48 AM UTC 2025

test-apps/electron-test/src/index.ts

@@ -756,7 +756,7 @@ class TimeSafariElectronTestApp {
     // Implementation would process items data and update local state
   }
 
-  private log(message: string, data?: Record<string, unknown>) {
+  private log(message: string, data?: Record<string, unknown>): void {
     const timestamp = new Date().toLocaleTimeString();
     const logEntry = document.createElement('div');
     logEntry.innerHTML = `<span class="timestamp">[${timestamp}]</span> ${message}`;