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, 7 insertions, 2 deletions

diff --git a/src/features/chat/ports.ts b/src/features/chat/ports.ts
index f8c665f..ffe2c94 100644
--- a/src/features/chat/ports.ts
+++ b/src/features/chat/ports.ts
@@ -1,12 +1,17 @@
 import type {
+	ChatQueueMessage,
 	ChatSendMessage,
 	ConversationHistoryResponse,
 	ConversationMetricsResponse,
 } from "@dispatch/transport-contract";
 
-/** Injected transport port — sends chat messages to the server. */
+/**
+ * Injected transport port — sends chat messages to the server. Accepts both
+ * `chat.send` (start a turn) and `chat.queue` (enqueue a steering message;
+ * auto-starts a turn if idle).
+ */
 export interface ChatTransport {
-	send(msg: ChatSendMessage): void;
+	send(msg: ChatSendMessage | ChatQueueMessage): void;
 }
 
 /**