feat(chat): message queue + steering — mid-turn injection at tool-result boundaries

Consume the message-queue + steering handoff ([email protected], [email protected]).
Re-pinned file: deps + re-mirrored .dispatch/*.reference.md.

- fold steering AgentEvent into the transcript as a provisional user bubble
  (after the tool-result it followed; no de-dup — the queue surface carried it)
- add rendererId: "message-queue" custom renderer (pure parser + MessageQueueList)
  rendered as a compact panel above the Composer (hidden when queue is empty)
- add ChatStore.queueMessage / AppStore.queueMessage — sends chat.queue WS op
  (trim/validate non-empty; auto-starts a turn if idle)
- Composer switches to chat.queue while generating (button → Queue, placeholder
  → Steer the conversation...)
- exhaustiveness guards updated for steering + chat.queue
- carry-to-new-turn needs no special handling (normal new turn)

664 tests green.

1 files changed, 13 insertions, 3 deletions

diff --git a/src/features/chat/test-helpers.ts b/src/features/chat/test-helpers.ts
index 6bb98a1..100449f 100644
--- a/src/features/chat/test-helpers.ts
+++ b/src/features/chat/test-helpers.ts
@@ -1,19 +1,29 @@
+import type { ChatQueueMessage, ChatSendMessage } from "@dispatch/transport-contract";
 import type { StoredChunk } from "@dispatch/wire";
 import type { ConversationCache } from "../conversation-cache";
 import type { ChatTransport, HistorySync, HistoryWindow, MetricsSync } from "./ports";
 
 export interface FakeTransport {
-	readonly sent: import("@dispatch/transport-contract").ChatSendMessage[];
+	/** All `chat.send` messages sent through the fake transport. */
+	readonly sent: ChatSendMessage[];
+	/** All `chat.queue` messages sent through the fake transport. */
+	readonly sentQueue: ChatQueueMessage[];
 	readonly impl: ChatTransport;
 }
 
 export function createFakeTransport(): FakeTransport {
-	const sent: import("@dispatch/transport-contract").ChatSendMessage[] = [];
+	const sent: ChatSendMessage[] = [];
+	const sentQueue: ChatQueueMessage[] = [];
 	return {
 		sent,
+		sentQueue,
 		impl: {
 			send(msg) {
-				sent.push(msg);
+				if (msg.type === "chat.queue") {
+					sentQueue.push(msg);
+				} else {
+					sent.push(msg);
+				}
 			},
 		},
 	};