Address remaining Gemini code review feedback

- Remove es5-ext from pnpm onlyBuiltDependencies (pure JS library doesn't need building)
- Add clarifying comment for WebSocket PING opcode (0x09) in frame test
- Error message handling for event objects already improved in earlier commits
- Manual counter tracking already eliminated through async/await refactoring

All review feedback has been addressed while maintaining test reliability.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: theturtle32

pnpm-workspace.yaml

@@ -1,5 +1,4 @@
 onlyBuiltDependencies:
   - bufferutil
-  - es5-ext
   - esbuild
   - utf-8-validate

test/unit/core/frame.test.mjs

@@ -14,7 +14,7 @@ describe('WebSocketFrame', () => {
       const frame = new WebSocketFrame(maskBytesBuffer, frameHeaderBuffer, {});
       frame.fin = true;
       frame.mask = true;
-      frame.opcode = 0x09; // WebSocketFrame.PING
+      frame.opcode = 0x09; // PING opcode
 
       let frameBytes;
       expect(() => {