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.

scripts/test-server.js

@@ -9,6 +9,9 @@
  * (including the pane the test was launched from). Dropping `TMUX` and
  * pointing `TMUX_TMPDIR` at a fresh directory gives every tmux call — the
  * app's own and the tests' direct `execFileSync("tmux", …)` — its own socket.
+ * It also points `DASHBOARD_PIPELINES_DIR` at `server/__tests__/fixtures/
+ * pipelines/`: AgentHub ships no pipeline template any more, and the two old
+ * ones kept there are what the dormant stage/detection code is tested against.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
@@ -26,7 +29,11 @@ const files = fs
 const args = process.argv.slice(2);
 
 const tmuxDir = fs.mkdtempSync(path.join(os.tmpdir(), "agenthub-test-tmux-"));
-const env = { ...process.env, TMUX_TMPDIR: tmuxDir };
+const env = {
+  ...process.env,
+  TMUX_TMPDIR: tmuxDir,
+  DASHBOARD_PIPELINES_DIR: path.join(dir, "fixtures", "pipelines"),
+};
 delete env.TMUX;
 delete env.TMUX_PANE;