Add active-turn steering (#3394)

* feat(agents): add active-turn steering

Let users choose whether an immediate prompt interrupts or joins the active turn. The daemon owns exact-turn admission, provider delivery, safe fallback, and canonical timeline identity while queueing remains client-side.

* fix(agents): stabilize steering history and replay QA

* fix(agents): preserve steering timeline order

* fix(agents): reconcile resumed provider history

* fix(agents): serialize steering with cancellation

* test(agents): prove Claude multi-tool steering

* test(agents): force explicit history hydration

* fix(agents): flush output before steer admission

packages/app/src/composer/input/input.tsx

@@ -131,7 +131,7 @@ export interface MessageInputProps {
   isAgentRunning?: boolean;
   /** Controls what the default send action (Enter, send button, dictation) does
    *  when the agent is running. "interrupt" sends immediately, "queue" queues. */
-  defaultSendBehavior?: "interrupt" | "queue";
+  defaultSendBehavior?: "interrupt" | "steer" | "queue";
   /** Callback for queue button when agent is running */
   onQueue?: (payload: MessagePayload) => void;
   /** Optional handler used when submit button is in loading state. */
@@ -1002,7 +1002,7 @@ interface SendButtonStateInput {
   isSubmitDisabled: boolean;
   isSubmitLoading: boolean;
   onSubmitLoadingPress: (() => void) | undefined;
-  defaultSendBehavior: "interrupt" | "queue";
+  defaultSendBehavior: "interrupt" | "steer" | "queue";
   isAgentRunning: boolean;
 }
 
@@ -1052,7 +1052,7 @@ interface ResolvedMessageInputProps {
   voiceServerId: string | undefined;
   voiceAgentId: string | undefined;
   isAgentRunning: boolean;
-  defaultSendBehavior: "interrupt" | "queue";
+  defaultSendBehavior: "interrupt" | "steer" | "queue";
   onQueue: ((payload: MessagePayload) => void) | undefined;
   onSubmitLoadingPress: (() => void) | undefined;
   onKeyPressCallback: ((event: { key: string; preventDefault: () => void }) => boolean) | undefined;
@@ -1608,6 +1608,7 @@ export const MessageInput = forwardRef<MessageInputRef, MessageInputProps>(
       submitButtonAccessibilityLabel,
       canPressLoadingButton,
       defaultActionQueues,
+      defaultSendBehavior,
       isAgentRunning,
       t,
     });