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.

INSTALL.md

@@ -33,9 +33,8 @@ dashboard, run it from source, or stay on Node 20.
 | Git | Any | Cloning the repository, and every lane operation (worktrees, branch/status reads) |
 | **tmux** | 3.x | **Required for the run console** — the browser terminal, `agenthub lanes shell`, and typing `/reload-plugins` into a live pane. See [Step 0](#step-0--system-packages) |
 | Codex CLI | Any | Optional — only for lanes whose tool is `codex` |
-| GitHub CLI (`gh`) | Any | Optional — only for `agenthub lanes ci status` and the PR stages of `/agenthub:ship-full` |
+| GitHub CLI (`gh`) | Any | Optional — only for `agenthub lanes ci status` |
 | Python | 3.6+ | Optional — only for `scripts/expand-ts-module-docs.py` (doc generation) |
-| `superpowers` plugin | Any | Optional — required only by `/agenthub:ship-feature` and `/agenthub:ship-feature-lane`, which drive its skills step by step (and which the built-in pipeline templates name as their per-node commands). Nothing else in AgentHub needs it; `/agenthub-doctor` reports it as `WARN` when absent. **Installed automatically** by the plugin's `SessionStart` bootstrap (opt out with `AGENTHUB_AUTO_INSTALL_PLUGINS=0`); by hand: `claude plugin install superpowers@claude-plugins-official` |
 
 ---
 
@@ -319,7 +318,6 @@ This repository includes extension packs for both Claude Code and Codex.
   - `CLAUDE.md`
   - `.claude/rules/`
   - `skills/` (shipped as the `agenthub` plugin's skills)
-  - `agents/` (shipped as the `agenthub` plugin's agents)
 - Codex project packs live under `.codex/`:
   - `AGENTS.md`
   - `.codex/rules/`