fix(app): resolve create agent dictation confirm handler timing issue

Fixed a state management bug where clicking the checkmark in create agent dictation mode would not trigger processing. The issue was that setIsDictationProcessing(true) was called after stopping the recorder, causing a race condition where the UI never showed the processing state.

Changes:
- Move setIsDictationProcessing(true) to execute immediately at the start of the confirm handler
- Add proper cleanup when audioData is null
- Ensure UI shows loading spinner when checkmark is clicked

This aligns the create agent dictation behavior with the working agent chat dictation implementation.

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

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

packages/app/src/components/create-agent-modal.tsx

@@ -983,16 +983,20 @@ function AgentFlowModal({
       );
       return;
     }
+
+    // Set processing state BEFORE stopping to ensure UI updates properly
+    setIsDictationProcessing(true);
+
     try {
       const audioData = await dictationRecorder.stop();
       setIsDictating(false);
       setDictationVolume(0);
       if (!audioData) {
+        setIsDictationProcessing(false);
         return;
       }
       const requestId = generateMessageId();
       dictationRequestIdRef.current = requestId;
-      setIsDictationProcessing(true);
       await sendAgentAudio(
         DICTATION_AGENT_ID,
         audioData,