huskies: merge 1090 refactor Migrate AgentPool::kill_all_children and kill_child_for_key to process_kill so server shutdown and stop_agent actually kill claude

server/src/agents/pool/stop.rs

@@ -71,8 +71,7 @@ impl AgentPool {
             self.kill_child_for_key(&key);
         }
 
-        // Step 3: now safe to mutate.  Status flip, handle abort, drop the
-        // child_killers entry.
+        // Step 3: now safe to mutate.  Status flip and handle abort.
         let (task_handle, tx) = {
             let mut agents = self.agents.lock().map_err(|e| e.to_string())?;
             let agent = agents
@@ -88,9 +87,6 @@ impl AgentPool {
             handle.abort();
             let _ = handle.await;
         }
-        if let Ok(mut killers) = self.child_killers.lock() {
-            killers.remove(&key);
-        }
 
         // Preserve worktree for inspection — don't destroy agent's work on stop.
         if let Some(ref wt) = worktree_info {