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/api/chat/types.ts

@@ -115,6 +115,12 @@ export type ServerMessage =
       type: 'result';
       sessionId: string;
       cost: MessageCost;
+      // Claude's OWN session uuid — the name of the transcript file under ~/.claude/projects/<slug>/.
+      // Distinct from `sessionId`, which is the key officer made up. Until this crossed the wire the
+      // platform had no way to address a session it had started: the mapping was captured inside the
+      // sidecar (claude-manager's setClaudeSession) and never left it. Absent if the harness didn't
+      // report one.
+      claudeSessionId?: string;
     }
   | {
       type: 'sync:messages';
@@ -177,6 +183,7 @@ export type ChatEvent =
   | {
       type: 'result';
       cost: MessageCost;
+      claudeSessionId?: string;
     }
   | { type: 'error'; message: string }
   | { type: 'stopped' }