feat(concurrency): loading-ring for queued chats (CR-13 consumed)

Backend shipped "queued" ConversationStatus (additive to [email protected]): when a
request blocks on a concurrency slot, conversation.statusChanged broadcasts
"queued" (broadcast-only, never persisted); "active" on slot grant.

FE consumes it:
- WS parser (adapters/ws/logic.ts): accepts "queued" in the status set.
- Store handler: "queued" updates the status map + opens a tab for a new
  cross-device queued conversation (like "active").
- TabList: status === "queued" -> loading-ring (spinner, aria-label "Queued");
  "active" -> loading-dots (unchanged).
- Composer: status type widened to ComposerStatus (idle|running|queued|error),
  exported from features/chat. "queued" -> a loading-ring status icon +
  placeholder "Queued for a slot…"; behaves like "running" for the send
  button (steer/stop — the turn is in flight, just waiting for a slot).
- App.svelte: composerStatus derived (error > queued > running > idle) —
  conversationStatus === "queued" wins over generating so the corner shows a
  ring during the wait (turn-start fires before the slot is granted, so
  generating is already true while status === "queued").
- Re-mirrored .dispatch/wire.reference.md (ConversationStatus widened + header).

Tests: WS parser accepts queued; store handler sets status + opens a cross-device
tab + transitions queued->active->idle; TabList renders a ring for queued + dots
for active. typecheck 0/0, 925 tests green (x2), biome clean, build OK.
backend-handoff.md CR-13 marked RESOLVED.

1 files changed, 15 insertions, 5 deletions

diff --git a/src/app/App.svelte b/src/app/App.svelte
index 5aa103d..b46885c 100644
--- a/src/app/App.svelte
+++ b/src/app/App.svelte
@@ -16,6 +16,7 @@
 		ModelSelector,
 		ReasoningEffortSelector,
 		type CompactNowResult,
+		type ComposerStatus,
 		type ReasoningEffortSaveResult,
 		type SaveCompactPercentResult,
 	} from "../features/chat";
@@ -238,6 +239,19 @@
 		return tab?.title ?? NEW_TAB_TITLE;
 	});
 
+	// The composer status-bar status. Priority: error > queued > running > idle.
+	// `queued` (the turn is in flight but waiting for a concurrency slot — CR-13)
+	// wins over `running` so the corner shows a ring, not dots, during the wait.
+	// `turn-start` fires before the slot is granted, so `generating` is already
+	// true while `conversationStatus === "queued"`; the explicit queued check is
+	// what distinguishes the two.
+	const composerStatus = $derived.by<ComposerStatus>(() => {
+		if (store.activeChat.error) return "error";
+		const id = store.activeConversationId;
+		if (id !== null && store.conversationStatus(id) === "queued") return "queued";
+		return store.activeChat.generating ? "running" : "idle";
+	});
+
 	// Conversation/tab switch → snap to the bottom of the new transcript.
 	$effect(() => {
 		void store.activeConversationId;
@@ -588,11 +602,7 @@
 			onStop={handleStop}
 			contextSize={store.activeChat.currentContextSize}
 			contextWindow={store.modelInfo[store.activeModel]?.contextWindow}
-			status={store.activeChat.error
-				? "error"
-				: store.activeChat.generating
-					? "running"
-					: "idle"}
+			status={composerStatus}
 		/>
 	</div>