fix(apiproxy): derive queued steering on the client, drop it from the wire

The session/queued frame no longer carries steering — AgentMessage no longer
has the field. The client derives it from the same ordered turn boundaries the
host saw (a frame arriving while a turn is open joined the steering FIFO).

packages/host/apiproxy/src/api-proxy.ts

@@ -384,7 +384,7 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
         let entries = queuedMirror.get(agent.id)
         if (entries === undefined) queuedMirror.set(agent.id, entries = new Map<AgentMessageId, AgentMessage>())
         entries.set(message.id, message)
-        broadcast({ type: 'session/queued', sessionId: agent.id, content: message.content, source: message.source, steering: message.steering })
+        broadcast({ type: 'session/queued', sessionId: agent.id, content: message.content, source: message.source })
       }),
       ctx.on('agent/inbox/dequeue', (agent: Agent, message: AgentMessage) => {
         retire(agent, message.id)
@@ -907,7 +907,7 @@ export function createApiProxy(ctx: Context, defaults: ApiProxyDefaults): ApiPro
         // queue view from these alone.
         for (const [sessionId, entries] of queuedMirror) {
           for (const entry of entries.values()) {
-            queue.push(frame({ type: 'session/queued', sessionId, content: entry.content, source: entry.source, steering: entry.steering }))
+            queue.push(frame({ type: 'session/queued', sessionId, content: entry.content, source: entry.source }))
           }
         }
         // Per-session open-call table for result-view pairing. Bounded by the

packages/host/apiproxy/src/api/events.schema.ts

@@ -36,7 +36,7 @@ export const muxFrameSchema = z.discriminatedUnion('type', [
   z.object({ type: z.literal('question/requested'), sessionId: sessionIdSchema, questions: z.array(askUserQuestionItemSchema).min(1) }),
   z.object({ type: z.literal('question/resolved'), sessionId: sessionIdSchema, questionRpcId: rpcIdSchema, outcome: z.union([z.literal('answered'), z.literal('cancelled')]) }),
   // content/source reuse the wide passthroughs (both are merge-extensible in core).
-  z.object({ type: z.literal('session/queued'), sessionId: sessionIdSchema, content: z.array(contentBlockSchema), source: z.looseObject({ kind: z.string() }), steering: z.boolean() }),
+  z.object({ type: z.literal('session/queued'), sessionId: sessionIdSchema, content: z.array(contentBlockSchema), source: z.looseObject({ kind: z.string() }) }),
   z.object({ type: z.literal('stream/error'), error: rpcErrorSchema }),
 ]) as unknown as z.ZodType<MuxFrame>
 

packages/host/apiproxy/src/api/events.ts

@@ -72,7 +72,7 @@ export type MuxFrame =
    * source carries the prompt's rpcId when the message came over this wire
    * (the client's provisional-echo reconciliation key).
    */
-  | { type: 'session/queued'; sessionId: SessionId; content: ContentBlock[]; source: MessageSource; steering: boolean }
+  | { type: 'session/queued'; sessionId: SessionId; content: ContentBlock[]; source: MessageSource }
   | { type: 'stream/error'; error: RpcError }
 
 /**