fix(codex-adapter): emit cancelled events on worker exit

Addressed review feedback about potential stream hangs when the Codex worker exits cleanly before emitting run results by injecting explicit cancelled and error events ahead of the iterator teardown. This ensures stream consumers always observe terminal metadata (cancelled + error + done) before the iterator finishes. Verified via npm run test --workspace examples.

Author: OhadAssulin

packages/codex-adapter/src/index.ts

@@ -395,7 +395,9 @@ export class CodexAdapter implements HeadlessCoder {
         push(DONE);
         return;
       }
-      push(createWorkerExitError(`Codex worker exited with code ${code}`, stderrOutput));
+      const reason = `Codex worker exited with code ${code}`;
+      push(createCancelledEvent(reason, stderrOutput));
+      push(createWorkerExitErrorEvent(reason, stderrOutput));
       push(DONE);
     });