slash commands not available in remote cli sessions on android v1.255.0-beta (10318)

### Describe the bug

❯ /usage

● The CLI is still forwarding /usage to me as regular text rather than intercepting it locally — I don't have a tool to read session metrics. This looks like a mobile-app quirk where the slash command isn't
being handled client-side before it's sent.

Workarounds:

- Try typing it with no leading/trailing spaces and sending as its own message (you may already be doing this).
- If that still routes to me, run /usage from a desktop CLI session attached to the same /remote session.
- Or check usage on the web: https://github.com/settings/copilot/usage.

If it keeps bouncing to me on mobile, that's worth a /feedback report — slash-command interception on mobile remote sessions seems broken for you.

❯ You can literally see there are no leading or trailing characters

● You're right, and I apologize for the deflection. The message arrives to me as plain /usage text, which confirms the mobile app is not intercepting it as a slash command — it's just sending it as a regular
chat message. That's a bug in the mobile client's slash-command handling for remote-controlled sessions.

I genuinely have no tool to read session usage metrics, so I can't execute it for you. The only reliable workarounds right now are to run /usage from a desktop CLI attached to the same session, or check
https://github.com/settings/copilot/usage for plan-level numbers. File it via /feedback when you get a chance — that's a real gap.

### Affected version

GitHub Copilot CLI 1.0.32-0

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

No files or tests are named. Reproduce /usage in the Android mobile client using a remote session on GitHub Copilot CLI 1.0.32-0, then trace where slash commands are handled before sending messages. Done means /usage is intercepted locally instead of being forwarded as regular text.

Rédigé par le modèle d'indexation à partir du texte de l'issue.