end a turn whose agent has gone

restarting officer-agent takes every persistent session with it and nothing
downstream notices: the browser's socket is healthy, officer's subscription is
a bus filter, and there is simply never another event. the spinner ran forever
and a refresh didn't help, because the transcript has no ending to read.

keyed off the agent *registering*, not disconnecting — a disconnect fires on
every `pm2 restart officer`, when the turn is fine. a registration socket dies
with its process, so an agent appearing on it is a new one. covers the sitting
tab; the reconnect path covers the rest, with the client now sending its belief
that a turn is in flight and officer checking it against the agent over a new
claude:is-generating. the check fails toward alive.

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

src/servers/sidecar/protocol.ts

@@ -17,6 +17,9 @@ export type SidecarCommand =
   | { type: 'claude:kill'; id: string; sessionKey: string }
   | { type: 'claude:interrupt'; id: string; sessionKey: string }
   | { type: 'claude:clear-session'; id: string; sessionKey: string }
+  // Is a turn still running for this session? Only the process that owns the session can say, which is
+  // exactly why it is asked over the wire — see `isClaudeGenerating` in sidecar-registry.
+  | { type: 'claude:is-generating'; id: string; sessionKey: string }
   // OpenCode — drive a turn via `opencode run … --format json` (tools re-anchored to cwd via --dir)
   | { type: 'opencode:run-streaming'; id: string; params: OpenCodeRunParams }
   | { type: 'opencode:kill'; id: string; sessionKey: string }
@@ -43,6 +46,7 @@ export type SidecarEvent =
   | { type: 'claude:killed'; id: string }
   | { type: 'claude:interrupted'; id: string }
   | { type: 'claude:session-cleared'; id: string }
+  | { type: 'claude:generating'; id: string; generating: boolean }
   // VNC
   | { type: 'vnc:started'; id: string; port: number; display: number }
   | { type: 'vnc:password'; id: string; password: string }