Open computers from the chat, let bots ask for a take-over, show task progress

- Serve each computer to its owner under /computers/<id>/ (HTTP and
  websockets proxied to the AIO sandbox) and show it in a shared
  ComputerView with browser, terminal and code modes, opened from the
  computers modal or a take-over button in the thread.
- ask_user_to_take_over lets a bot hand a computer to the user for a
  login or captcha; the message gets a take-over button and needs-you,
  and the viewer hands it back with a chat message.
- While a task runs the thread shows "<bot> is working..." with the
  task's latest step; steps read as plain words, not tool names.
- A coordinator with no workers no longer claims to delegate, and bots
  describe started tasks in the first person.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/harness/tools/bot/start-task-tool.ts

@@ -60,7 +60,7 @@ export default function startTaskTool({
                 computer_id: computer_id || undefined,
             });
 
-            return `Task #${job_id} queued. Tell the user you're on it; the result will be posted here when it's done.`;
+            return `Task #${job_id} queued; you'll work on it yourself in the background. Tell the user in one sentence, in the first person, what you're doing (e.g. "I'm checking your inbox now. I'll report back when I'm done."); the result will be posted here when it's done.`;
         },
     };
 }