Improve dictation UX: transcribe-only mode with UI fixes

- Dictation now appends transcribed text to input instead of auto-sending
- Voice button stays visible even with attachments or existing text
- Dictation works on create agent screen (not just agent chat)
- Input auto-grows when dictation appends text
- New agent screen input has solid background (no transparency)
- Timer preserves duration after confirming (no scary reset to zero)

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

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

packages/app/src/hooks/use-dictation.ts

@@ -320,6 +320,7 @@ export function useDictation(options: UseDictationOptions): UseDictationResult {
       pendingRequestIdRef.current = null;
       setPendingRequestId(null);
       setIsProcessing(false);
+      setDuration(0);
       setStatus("idle");
       setRetryAttempt(0);
       setRetryInfo(null);
@@ -493,7 +494,6 @@ export function useDictation(options: UseDictationOptions): UseDictationResult {
 
     setError(null);
     stopDurationTracking();
-    setDuration(0);
     setIsProcessing(true);
     setRetryInfo(null);
     setRetryAttempt(0);
@@ -566,6 +566,7 @@ export function useDictation(options: UseDictationOptions): UseDictationResult {
     pendingRequestIdRef.current = null;
     setPendingRequestId(null);
     setIsProcessing(false);
+    setDuration(0);
     setFailedRecording(null);
     setStatus("idle");
     setRetryAttempt(0);