chore(32-04): audit useState and add render counter

- Audited all 14 remaining useState declarations
- Documented decisions for each state variable
- Confirmed videoLoading/resyncLoading removed in Plan 03
- Identified 3 leave modal states as future colocation candidates
- Added temporary render counter for Phase 32 verification
- Counter logs only in development mode

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

jam-ui/src/components/client/JKSessionScreen.js

@@ -149,6 +149,14 @@ import attachIcon from '../../assets/img/client/attach.svg';
 import helpIcon from '../../assets/img/client/help.svg';
 
 const JKSessionScreen = () => {
+  // TEMPORARY: Render counter for Phase 32 verification
+  // Remove after verifying optimization
+  const renderCountRef = React.useRef(0);
+  renderCountRef.current += 1;
+  if (process.env.NODE_ENV === 'development') {
+    console.log(`[JKSessionScreen] Render #${renderCountRef.current}`);
+  }
+
   const logger = console; // Replace with another logging mechanism if needed
   const dispatch = useDispatch();
   const app = useJamKazamApp();