Agents: prompted about uncommitted changes on cloud session start, but Changes panel is empty

### Steps to Reproduce
1. Open the Agents window.
2. Select a remote repository.
3. Start a cloud session.
4. A prompt appears saying there are uncommitted changes and asks what to do with them.
5. Open the Changes panel to inspect them.

### Expected
I can see which files are dirty before deciding, either in the Changes panel or summarized/linked from the prompt itself.

### Actual

The Changes panel is empty (including when I swap to 'uncommitted changes'), so there's no way to find out what the uncommitted changes are. Without that context I risk discarding work I don't know about.

### Notes

Possibly related (both closed): #284089, #280456