feat(app): Enter key confirms and sends dictation

When dictating and focused on an agent, pressing Enter now confirms
the dictation and sends the message, matching the behavior of clicking
the submit button.

packages/app/src/components/message-input.tsx

@@ -100,7 +100,7 @@ export interface MessageInputProps {
 export interface MessageInputRef {
   focus: () => void;
   blur: () => void;
-  runKeyboardAction: (action: MessageInputKeyboardActionKind) => void;
+  runKeyboardAction: (action: MessageInputKeyboardActionKind) => boolean;
   /**
    * Web-only: return the underlying DOM element for focus assertions/retries.
    * May return null if not mounted or on native.
@@ -242,26 +242,35 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
     runKeyboardAction: (action) => {
       if (action === "focus") {
         textInputRef.current?.focus();
-        return;
+        return true;
+      }
+
+      if (action === "send" || action === "dictation-confirm") {
+        if (isDictatingRef.current) {
+          sendAfterTranscriptRef.current = true;
+          confirmDictation();
+          return true;
+        }
+        return false;
       }
 
       if (action === "voice-toggle") {
         handleToggleRealtimeVoiceShortcut();
-        return;
+        return true;
       }
 
       if (action === "voice-mute-toggle") {
         if (isRealtimeVoiceForCurrentAgent) {
           voice?.toggleMute();
         }
-        return;
+        return true;
       }
 
       if (action === "dictation-cancel") {
         if (isDictatingRef.current) {
           cancelDictation();
         }
-        return;
+        return true;
       }
 
       if (action === "dictation-toggle") {
@@ -271,7 +280,10 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(funct
         } else {
           void startDictationIfAvailable();
         }
+        return true;
       }
+
+      return false;
     },
     getNativeElement: () => {
       if (!IS_WEB) return null;