Review and act on working trees, branches and remotes from a Version Control panel

[Quicksaver]

Problem

Agents create branches, worktrees and commits faster than I can keep track of them. The Uncommitted diff and the commit dialog cover the current checkout's changes. To see which branches are ahead or behind, look at stashes, compare a branch with its base, browse history or deal with remote branches, I still open another Git client. On mobile, none of this is reachable. Related requests: #6941 (uncommitted overview), #6943 (history view), #10371 (select files and commit), #7162 (Git client built in).

Proposal

A Version Control surface in the right panel on web and desktop, plus a matching screen on mobile:

• Actionable: working trees with changes (including sibling worktrees), local branches ahead of or behind their upstream, stashes, and branches whose open PR is behind its base, each showing the existing PR badge.
• Actions on the selected item: commit or stash selected files, discard changes, apply, pop or drop a stash; check out, merge, rebase, pull, push, publish and delete a branch; undo or revert a commit; add and remove remotes; fetch. A diverged branch offers merge, force pull (reset to the upstream) or force push (--force-with-lease). Every destructive action asks for confirmation first.
• Git stays the source of truth: after every action, whether it succeeds or fails, the panel reloads its view from the repository, so a partial failure such as a conflict stays visible. Provider lookups (PR, avatars) are best-effort and respect rate-limit pauses, so a provider outage never hides Git-derived rows.

Interactive demo: https://quicksaver-piz.vercel.app/t3code/version-control-panel-work
Earlier implementation (closed pending this discussion): #12704

Suggested slices

#12704 was far too large to review in one go. I'd split it so each PR stands on its own:

1. A read-only panel on web and mobile: working trees and changed files, branches with ahead/behind, stashes, remotes, history and compare.
2. Working-tree actions: select files to commit or stash, discard, stash apply/pop/drop.
3. Branch and remote actions: checkout, delete, pull/push/rebase, fetch.
4. Optional and separate: when one project spans several connected environments, show one panel per environment.

Decisions I'd like maintainer sign-off on

1. Surface:
   • (my vote) its own right-panel surface?
   • or should this grow out of the existing Diff panel and Git actions control instead?
2. How far it goes as a Git client: is the action set above the right boundary? Is there anything you'd keep out of T3 Code entirely?
3. Background fetching: keeping remote branches current means fetching all remotes. I currently do this only while the panel is open, on its own interval following the existing background-activity policy, and with non-interactive credentials. Should that be on by default, or opt-in?
4. Mobile: in the first slice, or as a follow-up?

Out of scope

Worktree and branch naming (#6865, #6978), worktree cleanup (#6856), stacked PRs (#6995), Git marks in the Files tree (#7444), and project-wide graph visualisation (#12246).

Contribution

• I would be open to helping implement this.

If the direction works for you, I'll open the first slice scoped to whatever we agree on.