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__/WorkspaceHome.test.tsx

@@ -193,8 +193,9 @@ describe("freeSlot / paneRunId", () => {
   it("picks the first slot no live run of this lane holds", () => {
     expect(freeSlot(1, [])).toBe(0);
     expect(freeSlot(1, runs)).toBe(1);
-    const all = [0, 1, 2, 3].map((slot) => ({ laneId: 1, slot, status: "running" }) as RunHandle);
+    const all = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9].map((slot) => ({ laneId: 1, slot, status: "running" }) as RunHandle);
     expect(freeSlot(1, all)).toBeNull();
+    expect(freeSlot(1, all.slice(0, 4))).toBe(4);
     expect(freeSlot(2, all)).toBe(0);
     expect(paneRunId(4, 0)).toBe("agenthub-lane-4");
     expect(paneRunId(4, 2)).toBe("agenthub-lane-4-2");
@@ -318,7 +319,7 @@ describe("WorkspaceHome", () => {
     });
   });
 
-  it("says so when the server finds all four panes busy", async () => {
+  it("says so when the server finds all ten sessions in use", async () => {
     vi.mocked(api.lanes.action).mockRejectedValueOnce(
       Object.assign(new Error("every tab of this workspace is busy"), { code: "ERUNLIVE" })
     );
@@ -327,7 +328,7 @@ describe("WorkspaceHome", () => {
     await screen.findByTestId("workspace-recent-s-old");
     await user.type(screen.getByLabelText("How can I help you today?"), "go");
     await user.click(screen.getByTestId("workspace-home-start"));
-    expect(await screen.findByRole("alert")).toHaveTextContent("All four panes");
+    expect(await screen.findByRole("alert")).toHaveTextContent("All 10 sessions");
   });
 
   it("starts nothing on an empty prompt, and only once on a double Enter", async () => {