chat: carry claude's own session uuid on the result event

The sidecar knew which transcript file a turn had landed in and kept it to itself —
setClaudeSession fed --resume and nothing else. A session officer started was therefore
unaddressable from the platform side. Put it on the result event so it crosses the wire.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/sidecar/claude/stream-parser.ts

@@ -115,7 +115,9 @@ function handleResult(
     callbacks.onSessionId(sessionId);
   }
 
-  callbacks.onEvent({ type: 'result', cost });
+  // Carried on the event as well as into sidecar-local state: the callback only feeds `--resume` here,
+  // so without this the platform never learns which transcript file a session it started ended up in.
+  callbacks.onEvent({ type: 'result', cost, claudeSessionId: sessionId });
 }
 
 function handleSystem(msg: Record<string, unknown>, callbacks: StreamParserCallbacks): void {

src/servers/sidecar/claude/turn-stream.ts

@@ -67,7 +67,13 @@ export function createTurnStream(sessionId: string): TurnStream {
         ];
 
       case 'result':
-        return [...flush(), { msg: { type: 'result', sessionId, cost: event.cost }, durable: true }];
+        return [
+          ...flush(),
+          {
+            msg: { type: 'result', sessionId, cost: event.cost, claudeSessionId: event.claudeSessionId },
+            durable: true,
+          },
+        ];
 
       case 'error':
         return [{ msg: { type: 'error', message: event.message }, durable: true }];