Show the files a patch or pull request changed, each one openable in an editor #669

What problem does this address?

After you apply a patch or check out a pull request, the app says "X is applied, 3 files" and stops there. Unless you already know which files changed, you have to go looking for them. The same goes for your own work: files you added or edited on a ticket are only counted, never listed.

What is your proposed solution?

A section at the top of the site's right-hand sidebar that lists the changed files.

• Each file is a link with a file icon. One click opens it in the first detected editor (VS Code when it is installed), inside the site's workspace.
• With no editor detected, the click shows the file in Finder/Explorer instead.
• The notices on the left stay as they are.
• New UI uses WPDS (@wordpress/ui).

Planned as three stacked slices:

1. Applied patches. Built on add/affected-files-sidebar.
2. Checked-out pull requests. Built on add/affected-files-pr.
3. Your own changes. Planned. The section becomes Changed files, with two groups:
   • From the patch or From PR #N: the change's files. A file you edited after the change arrived is marked "also edited".
   • Your changes: files you added or edited that were not part of the patch or PR, with "new" on files you created. A fresh ticket with no patch or PR shows only this group.

Out of scope: a default-editor setting, per-file diffs, and marking deleted files in the patch list.

Design input needed

• Where the section sits in the sidebar: decided, at the top, above Details.
• How a long list (50+ files) should look: capped with "Show all", or left to the sidebar's own scrolling.
• Whether each file shows its full path, or its name with the directory muted.
• How the "also edited" and "new" markers should look beside a file.

Screenshots