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.

server/__tests__/lane-agents.test.js

@@ -1,7 +1,6 @@
 /**
- * @file Tests for lane-agents.js: agent-template installation into a lane's
- * .claude/agents/, including path resolution, git-exclude idempotence, and
- * missing-repo rejection.
+ * @file Tests for lane-agents.js's removeStageDoc and the codex pipeline
+ * cleanup it pairs with (clearCodexPipelines).
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -18,7 +17,7 @@ const { describe, it, after } = require("node:test");
 const assert = require("node:assert/strict");
 
 const lanesLib = require("../lib/lanes");
-const { installAgents, removeStageDoc } = require("../lib/lane-agents");
+const { removeStageDoc } = require("../lib/lane-agents");
 
 after(() => fs.rmSync(SUITE_ROOT, { recursive: true, force: true }));
 
@@ -48,87 +47,6 @@ function makeRepoDir() {
   return cwd;
 }
 
-/** Create a lane record backed by an existing directory. */
-function makeLane(cwd) {
-  return lanesLib.createLane({ title: "agents-test", cwd, kind: "managed" });
-}
-
-describe("installAgents", () => {
-  it("copies agent templates from agents/ dir into lane's .claude/agents/", async () => {
-    const cwd = makeRepoDir();
-    const lane = makeLane(cwd);
-    const result = await installAgents(lane);
-
-    assert.deepEqual([...result.installed].sort(), ["qc-local.md", "senior-gate-reviewer.md"]);
-    assert.ok(fs.existsSync(path.join(cwd, ".claude", "agents", "qc-local.md")));
-    assert.ok(fs.existsSync(path.join(cwd, ".claude", "agents", "senior-gate-reviewer.md")));
-
-    // Verify the source path is new (agents/) not old (data/agent-templates/)
-    const oldPath = path.join(__dirname, "..", "data", "agent-templates", "ship-feature-lane");
-    assert.equal(fs.existsSync(oldPath), false);
-  });
-
-  it("throws ENOTGITREPO when lane cwd has no .git", async () => {
-    const cwd = path.join(SUITE_ROOT, "no-git");
-    fs.mkdirSync(cwd, { recursive: true });
-    const lane = makeLane(cwd);
-    await assert.rejects(
-      () => installAgents(lane),
-      (err) => err.code === "ENOTGITREPO"
-    );
-  });
-
-  it("adds .claude/agents/ line to git info/exclude idempotently", async () => {
-    const cwd = makeRepoDir();
-    const lane = makeLane(cwd);
-
-    await installAgents(lane); // first
-    await installAgents(lane); // reinstall — should not duplicate
-
-    const excludePath = path.join(cwd, ".git", "info", "exclude");
-    const content = fs.readFileSync(excludePath, "utf8");
-    const matches = content.split("\n").filter((l) => l === ".claude/agents/");
-    assert.equal(matches.length, 1);
-  });
-
-  it("overwrites existing agents on reinstall", async () => {
-    const cwd = makeRepoDir();
-    const lane = makeLane(cwd);
-
-    await installAgents(lane);
-
-    // Tamper with the installed file
-    const agentPath = path.join(cwd, ".claude", "agents", "qc-local.md");
-    fs.writeFileSync(agentPath, "tampered");
-
-    // Reinstall
-    await installAgents(lane);
-    const content = fs.readFileSync(agentPath, "utf8");
-    assert.ok(content.includes("#"), "reinstalled file should look like markdown, not 'tampered'");
-    assert.notEqual(content, "tampered");
-  });
-
-  it("creates .claude/agents/ dir if it does not exist", async () => {
-    const cwd = makeRepoDir();
-    const lane = makeLane(cwd);
-    assert.equal(fs.existsSync(path.join(cwd, ".claude", "agents")), false);
-    await installAgents(lane);
-    assert.ok(fs.existsSync(path.join(cwd, ".claude", "agents")));
-  });
-
-  for (const tool of ["codex", "antigravity"]) {
-    it(`installs nothing for a ${tool} lane — no .claude/agents/, no AGENTS.md`, async () => {
-      const cwd = makeRepoDir();
-      const lane = lanesLib.createLane({ title: "cx", cwd, kind: "managed", tool });
-
-      const result = await installAgents(lane);
-      assert.deepEqual(result.installed, []);
-      assert.equal(fs.existsSync(path.join(cwd, ".claude", "agents")), false);
-      assert.equal(fs.existsSync(path.join(cwd, "AGENTS.md")), false);
-    });
-  }
-});
-
 describe("codex pipeline cleanup", () => {
   const START = "<!-- agenthub:stage:start -->";
   const END = "<!-- agenthub:stage:end -->";