feat(lanes): move the lane's git section into the Changes panel

- The branch line, the uncommitted-files hover panel and the git action
  row (fetch/pull/push/branch) move from the lane card to the top of the
  Changes panel (new LaneGitHeader.tsx); the card has no git row now.
- Header and panel share one git-facts read: stage/unstage/discard/commit
  and Refresh re-read it, and a git bar action re-reads the diff, the
  history and the file tree.
- The git bar no longer commits: the panel's staged-only box is the one
  commit path. Orphaned gitBar.commit*/cancel strings removed (en, vi).
- "New lane here" is wired from Workspace to the panel.

client/src/i18n/locales/en/lanes.json

@@ -169,15 +169,6 @@
   "gitBar.branchDelete": "Delete",
   "gitBar.branchDeleteHint": "Delete the selected branch (refused if it has unmerged commits)",
   "gitBar.branchNewPlaceholder": "New branch name…",
-  "gitBar.cancel": "Cancel",
-  "gitBar.commit": "Commit",
-  "gitBar.commitAll_one": "Commit {{count}} file",
-  "gitBar.commitAll_other": "Commit {{count}} files",
-  "gitBar.commitHint": "Stage everything and commit",
-  "gitBar.commitNothing": "Nothing to commit",
-  "gitBar.commitPlaceholder": "Commit message",
-  "gitBar.commitStaged": "Commit staged",
-  "gitBar.commitStagedHint": "Commit only what is staged in the Changes panel",
   "gitBar.fetch": "Fetch",
   "gitBar.fetchHint": "git fetch --all --prune",
   "gitBar.errNoRemote": "No remote to push to or pull from. Add one, or set this branch's upstream, in a terminal.",

client/src/i18n/locales/vi/lanes.json

@@ -169,15 +169,6 @@
   "gitBar.branchDelete": "Xoá",
   "gitBar.branchDeleteHint": "Xoá nhánh đang chọn (git từ chối nếu còn commit chưa merge)",
   "gitBar.branchNewPlaceholder": "Tên nhánh mới…",
-  "gitBar.cancel": "Huỷ",
-  "gitBar.commit": "Commit",
-  "gitBar.commitAll_one": "Commit {{count}} file",
-  "gitBar.commitAll_other": "Commit {{count}} file",
-  "gitBar.commitHint": "Stage tất cả rồi commit",
-  "gitBar.commitNothing": "Không có gì để commit",
-  "gitBar.commitPlaceholder": "Nội dung commit",
-  "gitBar.commitStaged": "Commit phần đã stage",
-  "gitBar.commitStagedHint": "Chỉ commit những file đã stage ở thẻ Changes",
   "gitBar.fetch": "Fetch",
   "gitBar.fetchHint": "git fetch --all --prune",
   "gitBar.errNoRemote": "Không có remote để push hoặc pull. Hãy thêm remote, hoặc đặt upstream cho nhánh này, trong terminal.",