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/hooks/use-keyboard-shortcuts.ts

@@ -129,6 +129,11 @@ export function useKeyboardShortcuts({
             id: "message-input.focus",
             scope: "message-input",
           });
+        case "send":
+          return keyboardActionDispatcher.dispatch({
+            id: "message-input.send",
+            scope: "message-input",
+          });
         case "dictation-toggle":
           return keyboardActionDispatcher.dispatch({
             id: "message-input.dictation-toggle",
@@ -139,6 +144,11 @@ export function useKeyboardShortcuts({
             id: "message-input.dictation-cancel",
             scope: "message-input",
           });
+        case "dictation-confirm":
+          return keyboardActionDispatcher.dispatch({
+            id: "message-input.dictation-confirm",
+            scope: "message-input",
+          });
         case "voice-toggle":
           return keyboardActionDispatcher.dispatch({
             id: "message-input.voice-toggle",