fix(ai-chat): record chats that fail on their first turn

Behaviour change (split out of the test commit per review).

In AI SDK v6 the useChat `onFinish` callback does NOT fire when the stream
errors. A brand-new chat whose very first turn fails would therefore never run
the post-turn path: the chat list was not invalidated and the client never
adopted the server-created chat id — so the failed chat only appeared in
history after a manual refresh (the server already creates the row and stores
the error message). Running the same `onTurnFinished()` handler on `onError`
makes the failed chat show up immediately. The error itself is still surfaced
to the user via the existing `error` state.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/client/src/features/ai-chat/components/chat-thread.tsx

@@ -134,6 +134,13 @@ export default function ChatThread({
     messages: initialMessages,
     transport,
     onFinish: () => onTurnFinished(),
+    // In AI SDK v6 `onFinish` does NOT fire when the stream errors, so a brand
+    // new chat that fails on its first turn would never invalidate the chat list
+    // nor adopt the server-created chat id (the server still creates the row and
+    // saves the error message). Run the same post-turn path on error so the
+    // failed chat appears in history immediately instead of after a manual
+    // refresh. The error itself is still surfaced via `error` below.
+    onError: () => onTurnFinished(),
   });
 
   const isStreaming = status === "submitted" || status === "streaming";