[FEATURE] Desktop app: show changes for every git repo a session touches in the diff pane

Problem

In the Claude desktop app (Code tab), when a session's working directory is a plain parent folder that contains several git repos (for example D:\Dev with repo-a/, repo-b/, repo-c/ inside it, each its own repo), the diff pane (Ctrl+Shift+D) shows nothing. The parent folder is not a git repo, so the pane has no repo to diff, even though the session is editing files in the repos underneath.

Cross-repo work is a common case, such as a schema change that touches an internal dashboard and a client-facing site together. Right now you have to choose between one session that has the full cross-repo context and separate per-repo sessions that have a working diff view.

Request

Have the diff pane detect every git repo under the session's working directories (including additional working directories) and show changes grouped by repo, for example as collapsible sections or a repo switcher, with the uncommitted / branch / commit scope applied per repo.

Environment

Claude desktop app, Code tab, Windows 11.