fix(#647): give the header-stats test app the input queue the constructor creates

Its prototype-only app had no _pendingDeliveries and only passed because the
removed try/catch swallowed the read. The real constructor always creates the
Map.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

test/header-stats-style.test.ts

@@ -69,6 +69,8 @@ beforeAll(async () => {
 function makeApp() {
   const app = Object.create(CodemanApp.prototype) as Record<string, any>;
   app.$ = (id: string) => document.getElementById(id);
+  // The constructor always creates the input queue; _updateConnectionIndicator reads it.
+  app._pendingDeliveries = new Map();
   return app;
 }