feat: workspace aliases, tab groups of split panes, native path picker (v2.1.0)

- /api/workspaces and `agenthub workspace(s)` / `--workspace` as aliases of
  /api/lanes and `agenthub lanes` / `--lane`; old names print one stderr note.
  REPL `help lanes|workspace|workspaces` resolves through the aliases.
- A workspace holds up to ten sessions (slots 0-9); every console tab is a
  group of 1-4 split panes (PaneGroups, agenthub.workspace.paneLayout);
  parseGroups keeps the stored active tab when an earlier one is dropped.
- Browse button beside path fields: POST /api/lanes/pick-path opens the OS
  picker on the server's desktop — loopback only and no forwarding header
  (EREMOTE), a display failure is ENODIALOG not a Cancel, the dialog is
  killed when the request closes, a folder field falls back to the in-app
  browser on any failure.
- Changes rail counts chip, image viewer (/git/raw), status bar session
  counts and per-day cost (`date=` on /api/pricing/cost).
- /agenthub-open and /agenthub-doctor run from the INSTALLED build
  (supersededBy), doctor offers fixes behind two confirmations; plugin-open
  treats a locked bootstrap as non-fatal.
- New-terminal shell waits for the first attach (issue #55).
- repo-onboarding / debug-live-issue skills removed.
- OpenAPI: pick-path, lane/date on /pricing/cost, tool on /run/history,
  /api/workspaces mount.

client/src/components/lanes/__tests__/AddLaneModal.test.tsx

@@ -26,6 +26,7 @@ vi.mock("../../../lib/api", () => ({
       worktree: vi.fn(),
       ensure: vi.fn(),
       browse: vi.fn(),
+      pickPath: vi.fn(),
       get: vi.fn(),
       profileInit: vi.fn(),
       mcpSync: vi.fn(),
@@ -147,6 +148,7 @@ beforeEach(() => {
   vi.mocked(api.lanes.worktree).mockReset();
   vi.mocked(api.lanes.ensure).mockReset();
   vi.mocked(api.lanes.browse).mockReset();
+  vi.mocked(api.lanes.pickPath).mockReset();
   // Provisioning finishes instantly by default - tests that care about the
   // provisioning-in-progress race override this per-test.
   vi.mocked(api.lanes.get)
@@ -549,7 +551,45 @@ describe("AddLaneModal — repo mode (adopt)", () => {
 });
 
 describe("AddLaneModal — folder browse", () => {
+  const noNativePicker = () =>
+    vi
+      .mocked(api.lanes.pickPath)
+      .mockRejectedValue(Object.assign(new Error("no picker"), { code: "ENODIALOG" }));
+
+  it("fills the path field from the OS's own picker", async () => {
+    vi.mocked(api.lanes.pickPath).mockResolvedValue({ path: "/Users/tester/app" });
+    renderModal();
+    const user = userEvent.setup();
+
+    await user.click(screen.getByTitle("Browse for a folder"));
+
+    await waitFor(() =>
+      expect(document.getElementById("add-lane-repo")).toHaveValue("/Users/tester/app")
+    );
+    expect(api.lanes.browse).not.toHaveBeenCalled();
+  });
+
+  it("falls back to the in-app browser when no native picker is available", async () => {
+    noNativePicker();
+    vi.mocked(api.lanes.browse).mockResolvedValue({
+      path: "/Users/tester",
+      parent: null,
+      entries: [],
+    });
+    const onClose = vi.fn();
+    renderModal({ onClose });
+    const user = userEvent.setup();
+
+    await user.click(screen.getByTitle("Browse for a folder"));
+    const browser = await screen.findByRole("dialog", { name: "Browse for a folder" });
+    // Its backdrop closes only the browser, never the modal behind it.
+    await user.click(browser.parentElement!);
+    expect(screen.queryByRole("dialog", { name: "Browse for a folder" })).toBeNull();
+    expect(onClose).not.toHaveBeenCalled();
+  });
+
   it("opens the browser, lists subdirectories, and selecting one fills the path field", async () => {
+    noNativePicker();
     vi.mocked(api.lanes.browse).mockResolvedValue({
       path: "/Users/tester",
       parent: "/Users",
@@ -566,6 +606,7 @@ describe("AddLaneModal — folder browse", () => {
   });
 
   it("Escape closes only the folder browser, not the whole modal", async () => {
+    noNativePicker();
     vi.mocked(api.lanes.browse).mockResolvedValue({
       path: "/Users/tester",
       parent: null,