Desktop app: folder picker has no path input, and the diff pane is empty when the session root is not the edited git repo

Summary

Two related papercuts in the desktop app's Code tab around the session's working directory.

1. The "change folder" control only offers a native folder picker. There is no way to type or paste a path. Navigating a deep monorepo layout (~/Workspaces/<org>/repos/<owner>/<repo> plus git worktrees next to the clone) through the picker is slow, and worktree folders are easy to confuse with the main clone. The underlying change_directory tool already accepts an exact path and shows a one-click approval for it, so the capability exists; the UI just does not expose a text field.

2. The diff pane shows "No changes to show" whenever the session root is not the git repository being edited. A session started in a parent folder that is not a repo (~/Workspaces), with all edits happening in a repo or worktree a few levels below, renders an empty pane even after several commits on the branch. There is no hint about why. Moving the session root into the repo fixes it, but the move only takes effect at the end of the current turn, so the pane stays empty for one more message.

Steps to reproduce

1. Start a Code tab session in a folder that is not a git repository (e.g. ~/Workspaces).
2. Have Claude create a git worktree under it and commit changes there.
3. Open the diff pane: "No changes to show".
4. Click the folder control to move the session: only a picker appears, no path input.

Expected

• A path field (or paste support) next to the picker, matching what the change_directory tool already accepts.
• The diff pane either follows the repository of the files that were edited, or explains that the session root is not a git repository and offers to move it.

Environment

• Claude desktop app 2.2553.0 (macOS, Darwin 25.6.0)
• Claude Code 2.1.241

Workaround for others hitting this: ask Claude to call change_directory with the exact path; the app then shows a plain approval dialog for that folder instead of the picker.

Start by tracing the desktop app's Code tab folder control and diff pane, then compare their behavior with the existing change_directory tool and its approval flow. Done means users can enter or paste a path, and the diff pane either follows the edited repository or explains why the session root cannot provide a diff.