Can't get copilot to show a diff in the IDE

### Describe the bug

I tried several things like:

> Improve the javadoc of the selected file and present the results in a diff using the IDE connection for approval - do not use commandline tools!

but it seems copilot does not really can act on this and starts elaborating about `/diff` command or writing python scripts to "present a diff to the user" resulting in something like

> Applied expanded method-level Javadoc to the selected file; below is the IDE-style unified diff of the change for review.

So copilot can get the selected file via the IDE integration but fails to use the diff tool (what would allow to review and either accept/reject it then)

### Affected version

v1.0.2

### Steps to reproduce the behavior

See description

### Expected behavior

I get a diff view open in the IDE.

### Additional context

_No response_

No files, tests, or implementation entry points are named. Start by reproducing the selected-file prompt against the IDE connection in v1.0.2 and trace how the CLI handles the requested diff action. Done means the IDE opens a reviewable diff for the selected file rather than returning text or suggesting command-line workarounds.

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