Improve descriptions of agents

[bpasero]

We show a hover next to the session type from @benibenj new dropdown:

We should improve it to make it clear per session when to use what. Relevant code pointer:

https://github.com/microsoft/vscode-distro/blob/b90415e4e25274537a83463c7af88fca7e9528a7/mixin/exploration/product.json#L2675-L2698

I think the Cloud one is good enough, would be great to add and improve for the others.

For background we need to talk about worktree and thus isolation.

[ntrogh]

Suggestions and questions:

• Local
  • Run tasks within VS Code chat. The agent iterates via chat and works interactively to implement changes on your main workspace.
  • When you already have an active local session, this option is currently a no-op. Is there a scenario where you delegate to a local session? If not, what is the purpose of this action?
• Background
  • Delegate tasks to a background agent running locally on your machine. The agent iterates via chat and works asynchronously in a Git worktree to implement changes isolated from your main workspace.
  • Should we mention that we're delegating to GitHub Copilot CLI, or do we consider this an implementation detail?
• Cloud
  • Delegate tasks to the GitHub Copilot coding agent. The agent iterates via chat and works asynchronously in the cloud to implement changes and pull requests as needed. (afaik, the official name GitHub Copilot coding agent?)
• Claude
  • Delegate tasks to the Claude Code agent running locally on your machine. The agent iterates via chat and works asynchronously to implement changes.
  • Does Claude Code start a worktree to isolate changes?
• Codex
  • Delegate tasks to the Codex agent running locally on your machine. The agent iterates via chat and works asynchronously to implement changes.
  • Does Codex use a worktree to isolate changes?

[benibenj]

I kind of have the implementation, but I'm waiting for Megan to get her PR merged first as she started this.
MY PR
HER PR