fix(tui): drain message queue on every busy → false transition

Previously the queue only drained inside the message.complete event
handler, so anything enqueued while a shell.exec (!sleep, !cmd) or a
failed agent turn was running would stay stuck forever — neither of
those paths emits message.complete. After Ctrl+C an interrupted
session would also orphan the queue because idle() flips busy=false
locally without going through message.complete.

Single source of truth: a useEffect that watches ui.busy. When the
session is settled (sid present, busy false, not editing a queue
item), pull one message and send it. Covers agent turn end,
interrupt, shell.exec completion, error recovery, and the original
startup hydration (first-sid case) all at once.

Dropped the now-redundant dequeue/sendQueued from
createGatewayEventHandler.message.complete and the accompanying
GatewayEventHandlerContext.composer field — the effect handles it.

ui-tui/src/app/createGatewayEventHandler.ts

@@ -46,7 +46,6 @@ const pushNote = pushUnique(6)
 const pushTool = pushUnique(8)
 
 export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev: GatewayEvent) => void {
-  const { dequeue, queueEditRef, sendQueued } = ctx.composer
   const { rpc } = ctx.gateway
   const { STARTUP_RESUME_ID, newSession, resumeById, setCatalog } = ctx.session
   const { bellOnComplete, stdout, sys } = ctx.system
@@ -394,16 +393,6 @@ export function createGatewayEventHandler(ctx: GatewayEventHandlerContext): (ev:
           patchUiState(state => ({ ...state, usage: { ...state.usage, ...ev.payload!.usage } }))
         }
 
-        if (queueEditRef.current !== null) {
-          return
-        }
-
-        const next = dequeue()
-
-        if (next) {
-          sendQueued(next)
-        }
-
         return
       }
 

ui-tui/src/app/interfaces.ts

@@ -193,11 +193,6 @@ export interface InputHandlerResult {
 }
 
 export interface GatewayEventHandlerContext {
-  composer: {
-    dequeue: () => string | undefined
-    queueEditRef: MutableRefObject<null | number>
-    sendQueued: (text: string) => void
-  }
   gateway: GatewayServices
   session: {
     STARTUP_RESUME_ID: string

ui-tui/src/app/useMainApp.ts

@@ -380,12 +380,13 @@ export function useMainApp(gw: GatewayClient) {
     sys
   })
 
-  const prevSidRef = useRef<null | string>(null)
+  // Drain one queued message whenever the session settles (busy → false):
+  // agent turn ends, interrupt, shell.exec finishes, error recovered, or the
+  // session first comes up with pre-queued messages. Without this, shell.exec
+  // and error paths never emit message.complete, so anything enqueued while
+  // `!sleep` / a failed turn was running would stay stuck forever.
   useEffect(() => {
-    const prev = prevSidRef.current
-    prevSidRef.current = ui.sid
-
-    if (prev !== null || !ui.sid || ui.busy || composerRefs.queueEditRef.current !== null) {
+    if (!ui.sid || ui.busy || composerRefs.queueEditRef.current !== null) {
       return
     }
 
@@ -416,7 +417,6 @@ export function useMainApp(gw: GatewayClient) {
   const onEvent = useMemo(
     () =>
       createGatewayEventHandler({
-        composer: { dequeue: composerActions.dequeue, queueEditRef: composerRefs.queueEditRef, sendQueued },
         gateway,
         session: {
           STARTUP_RESUME_ID,
@@ -432,11 +432,8 @@ export function useMainApp(gw: GatewayClient) {
     [
       appendMessage,
       bellOnComplete,
-      composerActions,
-      composerRefs,
       gateway,
       panel,
-      sendQueued,
       session.newSession,
       session.resetSession,
       session.resumeById,