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/i18n/resources/en.ts

@@ -94,6 +94,7 @@ export const en = {
       interruptAgent: "Interrupt agent",
       queueMessage: "Queue message",
       sendAndInterrupt: "Send and interrupt",
+      sendAndSteer: "Send and steer",
       sendMessage: "Send message",
       queue: "Queue",
       send: "Send",
@@ -1890,10 +1891,13 @@ export const en = {
         label: "Default send",
         descriptions: {
           interrupt: "When the agent is running, Enter interrupts. Command/Ctrl+Enter queues.",
+          steer:
+            "When the agent is running, Enter steers the active turn. Command/Ctrl+Enter queues.",
           queue: "When the agent is running, Enter queues. Command/Ctrl+Enter submits.",
         },
         options: {
           interrupt: "Interrupt",
+          steer: "Steer",
           queue: "Queue",
         },
       },