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/components/lanes/__tests__/LaneChangesPanel.test.tsx

@@ -20,6 +20,8 @@ import type { LaneChanges } from "../../../lib/types";
 vi.mock("../../../lib/api", () => ({
   api: {
     lanes: {
+      git: vi.fn(),
+      gitBranches: vi.fn(),
       changes: vi.fn(),
       gitAction: vi.fn(),
       gitLog: vi.fn(),
@@ -77,6 +79,7 @@ function changes(over: Partial<Extract<LaneChanges, { available: true }>> = {}):
 }
 
 beforeEach(() => {
+  vi.mocked(api.lanes.git).mockReset().mockResolvedValue({ available: false });
   vi.mocked(api.lanes.changes).mockReset();
   vi.mocked(api.lanes.changes).mockResolvedValue(changes());
   vi.mocked(api.lanes.gitAction).mockReset();
@@ -213,6 +216,73 @@ describe("LaneChangesPanel", () => {
     });
   });
 
+  it("heads the panel with the lane's git line, and a stage re-reads it", async () => {
+    vi.mocked(api.lanes.git).mockResolvedValue({
+      available: true,
+      branch: "feat/thing",
+      head: "9b3e74a",
+      subject: "wip",
+      dirty: 2,
+      untracked: 1,
+      files: [],
+      hasRemote: false,
+      upstream: null,
+      ahead: null,
+      behind: null,
+    });
+    const user = userEvent.setup();
+    render(<LaneChangesPanel laneId={7} />);
+    expect(await screen.findByTestId("lane-git")).toHaveTextContent("feat/thing");
+    expect(screen.getByTestId("lane-git-bar")).toBeInTheDocument();
+    expect(api.lanes.git).toHaveBeenCalledTimes(1);
+
+    const [stage] = screen.getAllByRole("button", { name: "Stage this file" });
+    await user.click(stage!);
+    // The header's counts moved with the index: waiting out its 30s poll
+    // would leave them wrong beside the list that just changed.
+    await waitFor(() => expect(api.lanes.git).toHaveBeenCalledTimes(2));
+  });
+
+  it("re-reads the diff after a git bar action", async () => {
+    vi.mocked(api.lanes.git).mockResolvedValue({
+      available: true,
+      branch: "feat/thing",
+      head: "9b3e74a",
+      subject: "wip",
+      dirty: 0,
+      untracked: 0,
+      files: [],
+      hasRemote: true,
+      upstream: "origin/feat/thing",
+      ahead: 0,
+      behind: 1,
+    });
+    const user = userEvent.setup();
+    render(<LaneChangesPanel laneId={7} />);
+    await screen.findByTestId("lane-git-bar");
+    const before = vi.mocked(api.lanes.changes).mock.calls.length;
+
+    await user.click(screen.getByRole("button", { name: /Pull/ }));
+    expect(api.lanes.gitAction).toHaveBeenCalledWith(7, "pull", {});
+    // A pull rewrites the working tree the list below describes.
+    await waitFor(() =>
+      expect(vi.mocked(api.lanes.changes).mock.calls.length).toBeGreaterThan(before)
+    );
+  });
+
+  it("re-reads history too when Refresh is pressed there", async () => {
+    const user = userEvent.setup();
+    render(<LaneChangesPanel laneId={7} />);
+    await screen.findByTestId("lane-changes-overview");
+    await user.click(screen.getByRole("button", { name: "History" }));
+    await screen.findByText("feat: the commit");
+    vi.mocked(api.lanes.gitLog).mockClear();
+
+    await user.click(screen.getByRole("button", { name: "Refresh" }));
+    // A pull or a switch from the git bar moves the commit list as well.
+    await waitFor(() => expect(api.lanes.gitLog).toHaveBeenCalledTimes(1));
+  });
+
   it("needs two clicks to discard, and only the second one reaches the server", async () => {
     const user = userEvent.setup();
     render(<LaneChangesPanel laneId={7} />);