Agents app UX: Include a total diff # in UI

[jo-oikawa]

From feedback from @lszomoru ...

We've removed the total diff number from the information in the title bar to clean up that space, but it still helps provide a high level overview of the scope/size of changes.

Is there a spot we can include this information within the changes panel or chat output? Is there a better way we can include this in the title bar or sessions list?

[vs-code-engineering]

Hi @jo-oikawa. As a member of the team, you can help us triage this issue by referring to https://github.com/microsoft/vscode-copilot/wiki/Copilot-Inbox-Tracker and assigning an owner directly.