stop the harness before deleting its transcript, and wait for it to actually stop

Deleting a commander removed its transcript and the `claude` CLI wrote it
straight back. Verified rather than inferred: the file returned with 22 lines,
every one timestamped after the delete, and the deleted commander was sitting in
/chat as "(untitled)" — no longer in `command_hq_sessions`, so nothing filtered
it out. Delete a commander, get an untitled chat back.

Two causes, and the first one hid the second.

The kill never happened. `killClaudeSession` was imported straight from
`claude-manager` into a route that runs in `officer`, while the session map lives
in `officer-claude-code`. It read an empty map in the wrong process and returned
false every time. `claude:kill` and `killClaude` already existed for this; the
route just wasn't using them.

And killing is not being dead. `abort()` returns while the CLI is still
unwinding, and officer does not own that file — the CLI does. So a session now
carries an `exited` promise resolved by the same exit hook that already reaps it,
`claude:kill` replies only once that resolves, and both delete routes await the
reply before touching the filesystem.

Bounded at 5s and never fatal. A child that will not die delays a delete by
seconds instead of hanging it, and a sidecar that is down leaves the caller with
exactly the race it already had.

`markExited` fires before `dropDeadSession`'s identity guard, deliberately: a
waiter has to be released even when a newer session has taken its key, or it
blocks for the full timeout on a process that died on schedule.

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

src/servers/sidecar/claude/user-instance.ts

@@ -294,11 +294,20 @@ async function handleCommand(cmd: SidecarCommand, reply: ReplyFn) {
       break;
     }
 
-    case 'claude:kill':
-      claudeManager.killClaudeSession(cmd.sessionKey, cmd.userId);
+    case 'claude:kill': {
+      /*
+        Reply only once the child is actually gone.
+      
+        The caller deleting a session's transcript has to know the CLI has stopped writing it, and this
+        reply is the only signal it can get — officer's side of the socket has no view of the process.
+        Bounded inside `killClaudeSessionAndWait`, so a child that will not die delays this by seconds
+        rather than hanging the caller's request.
+      */
+      await claudeManager.killClaudeSessionAndWait(cmd.sessionKey, cmd.userId);
       sessionLog.drop(cmd.sessionKey);
       reply({ type: 'claude:killed', id: cmd.id });
       break;
+    }
 
     case 'claude:interrupt':
       await claudeManager.interruptClaudeSession(cmd.sessionKey, cmd.userId);