[FEATURE] Allow sending a fresh (zero-message) session to the background / agent view without first exchanging a message

Summary

You cannot move a freshly-launched interactive session into the background (agent view) until at least one message has been exchanged with it. The "send to background" action (the ← action in the agent view) is disabled/blocked on a session that has had no communication.

The friction

To get a brand-new session into the agent view, you're forced to:

1. Type a throwaway message (e.g. "wait a second") just to unlock the action.
2. Wait for the model to respond — burning time and tokens on a reply you don't want or need.
3. Then finally send it to the background.

It's an absurd little dance for something that should be a single immediate action. Every new agent I want to register in the view costs me a pointless prompt, a pointless wait, and a pointless response before I can do the one thing I actually wanted — put it in the background. The cost compounds every single time, because there's no way to register an agent in the view without going through it.

Why I want this

I launch claude inside a project directory specifically so the session boots with the correct project context (project CLAUDE.md, .claude/ skills, per-project MCP config, correct cwd). I then want to push that session straight into the agent view so I can @-mention it for future tasks. Launching in the project dir and backgrounding is the only reliable way to get an agent into the view with the correct project context — and the zero-message gate adds needless friction to that exact workflow.

Steps to reproduce

1. In a project directory, run claude to start an interactive session.
2. Without sending any message, attempt to send the session to the background (← in the agent view).
3. The action is unavailable/blocked.
4. Type any message (e.g. "wait a second"), wait for a response.
5. The "send to background" action now works.

Expected behavior

A freshly-started session can be sent to the background / registered in the agent view immediately, with zero messages exchanged.

Actual behavior

Backgrounding is gated on having exchanged at least one message, forcing a throwaway message + a full model round-trip before the session can be backgrounded.

Environment

• Claude Code v2.1.181
• macOS (Darwin 25.5.0)