Should `#openPullRequest` consider diff editor?

[bamurtaugh]

Testing #7714

• Check out a PR
• Diff view opens
• Ask Copilot Chat what is the status of #openPullRequest
• I get the following:
  • 
  • 
• ❔ A few things I might expect instead:
  • The diff view being open to count as an open PR
  • Or, if we don't want to count the diff view, I'd expect the tool result to say No open pull request rather than No active pull request

[alexr00]

Good idea!

[alexr00]

To verify:

• Install the latest pre-release version of the extension
• Open a clone of a GitHub repo in VS Code
• Don't have a PR checked out.
• Open the Pull Request view, and expand a PR there to view it's files. Open one of the file diffs.
• Open the Chat view and ask Chat something about the #openPullRequest. Verify that it understands which PR you're asking about.

[bamurtaugh]

This works great - verified, thank you!

This testing inspired another feature request: #7889.