refactor(lanes): drop the workflow skills and Superpowers link; pipelines go dormant

The plugin stops shipping its workflow layer:
- skills/ship-feature and skills/ship-feature-lane, the 18 stage/ship slash
  commands (plugin.json keeps agenthub-doctor/update/open), and all four
  agents/ (qc-local, senior-gate-reviewer, backend-reviewer, frontend-reviewer).
- CLI `agenthub skills install`, `agenthub lanes agents install`,
  `agenthub ship-full|ship-quick`; routes POST /api/skills/install and
  POST /api/lanes/:id/agents/install; the Settings button, the lane Tools
  menu item and the Add-lane setup step that called them.
- The Superpowers auto-install: server/lib/skill-plugins.js, the bootstrap's
  autoInstallSkillPlugins / skillPluginsSettled gate and the doctor row.

Pipelines are kept but dormant: server/data/pipelines/ is deleted, so no
template ships. `default` resolves to EMPTY_PIPELINE (no nodes, progress 0),
createLane still accepts it, POST /api/lanes/:id/stage answers 400
ENOPIPELINE, and the Workspace hides the stage timer, pickers, PipelineMap
and strip stage chip for a lane with no nodes. A template dropped into
DASHBOARD_PIPELINES_DIR turns it all back on. The server suite loads its
templates from server/__tests__/fixtures/pipelines/.

Docs: CLAUDE.md (marker, retired rules), README(.vi), INSTALL, ARCHITECTURE,
docs/LANES|PLUGINS|CLI|API, agenthub-introduction.html.

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

@@ -27,7 +27,6 @@ vi.mock("../../../lib/api", () => ({
       browse: vi.fn(),
       get: vi.fn(),
       profileInit: vi.fn(),
-      agentsInstall: vi.fn(),
       mcpSync: vi.fn(),
       routerApply: vi.fn(),
     },
@@ -120,7 +119,6 @@ beforeEach(() => {
   vi.mocked(api.lanes.profileInit)
     .mockReset()
     .mockResolvedValue({ scaffolded: false, reason: "no detectable Node.js project" });
-  vi.mocked(api.lanes.agentsInstall).mockReset().mockResolvedValue({ installed: [] });
   vi.mocked(api.lanes.mcpSync).mockReset().mockResolvedValue({ servers: [], profilesSeeded: [] });
   vi.mocked(api.lanes.routerApply).mockReset().mockResolvedValue({
     tool: "claude",
@@ -383,7 +381,7 @@ describe("AddLaneModal — worktree mode (default)", () => {
     expect(screen.queryByRole("dialog")).toBeNull();
   });
 
-  it("fires profileInit, agentsInstall, and mcpSync after a successful worktree call", async () => {
+  it("fires profileInit and mcpSync after a successful worktree call", async () => {
     vi.mocked(api.lanes.branches).mockResolvedValue({
       branches: ["main"],
       current: "main",
@@ -401,7 +399,6 @@ describe("AddLaneModal — worktree mode (default)", () => {
 
     await waitFor(() => expect(api.lanes.worktree).toHaveBeenCalled());
     await waitFor(() => expect(api.lanes.profileInit).toHaveBeenCalledWith(42));
-    expect(api.lanes.agentsInstall).toHaveBeenCalledWith(42);
     expect(api.lanes.mcpSync).toHaveBeenCalledWith(42);
     await waitFor(() => expect(onAdded).toHaveBeenCalled());
   });
@@ -416,7 +413,6 @@ describe("AddLaneModal — worktree mode (default)", () => {
       lane: { id: 43, title: "demo2", cwd: "/lanes/demo2", status: "provisioning" } as Lane,
     });
     vi.mocked(api.lanes.profileInit).mockRejectedValue(new Error("boom"));
-    vi.mocked(api.lanes.agentsInstall).mockRejectedValue(new Error("boom"));
     vi.mocked(api.lanes.mcpSync).mockRejectedValue(new Error("boom"));
     const onAdded = vi.fn();
     const onClose = vi.fn();
@@ -482,7 +478,6 @@ describe("AddLaneModal — worktree mode (default)", () => {
     await waitFor(() => expect(onAdded).toHaveBeenCalled());
     expect(await screen.findByText(/auto-setup was skipped/)).toBeInTheDocument();
     expect(api.lanes.profileInit).not.toHaveBeenCalled();
-    expect(api.lanes.agentsInstall).not.toHaveBeenCalled();
     expect(api.lanes.mcpSync).not.toHaveBeenCalled();
   });
 });

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

@@ -23,7 +23,6 @@ vi.mock("../../../lib/api", () => ({
       up: vi.fn(),
       down: vi.fn(),
       preflight: vi.fn().mockResolvedValue({ blocked: [], warnings: [] }),
-      agentsInstall: vi.fn(),
       mcpSync: vi.fn(),
       syncBaseCheck: vi.fn(),
       routerApply: vi.fn(),
@@ -309,17 +308,6 @@ describe("LaneToolsMenu", () => {
     } as unknown as LaneRuntime);
   });
 
-  it("clicking Install agents calls the API and shows the result", async () => {
-    vi.mocked(api.lanes.agentsInstall).mockResolvedValue({
-      installed: ["qc-local.md", "senior-gate-reviewer.md"],
-    });
-    render(<LaneToolsMenu lane={makeLane()} />);
-    await userEvent.click(await screen.findByTestId("lane-tools-menu"));
-    await userEvent.click(await screen.findByTestId("lane-agents-install"));
-    await waitFor(() => expect(api.lanes.agentsInstall).toHaveBeenCalledWith(1));
-    expect(await screen.findByTestId("lane-action-result")).toHaveTextContent("qc-local.md");
-  });
-
   it("clicking Sync MCP calls the API and shows the result", async () => {
     vi.mocked(api.lanes.mcpSync).mockResolvedValue({
       servers: ["playwright"],