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/lib/lane-agents.js

@@ -1,24 +1,11 @@
 /**
- * @file Installs a `claude` lane's driving instructions: the
- * ship-feature-lane pipeline's agent templates
- * (qc-local, senior-gate-reviewer) into a lane's own .claude/agents/, so a
- * driving session can launch them by the BARE subagent_type name. Source is
- * the repo's own `agents/` — the same files the agenthub plugin ships, where
- * they resolve as `agenthub:qc-local`; installing them into the lane is what
- * makes the unprefixed name work there too. Plain file I/O except
- * for one git call — resolving where a worktree lane's shared info/exclude
- * actually lives, the same git-dir/git-common-dir distinction E2's
- * lane-sync.js had to get right for info/attributes.
+ * @file Cleans up what older builds wrote into a lane: `removeStageDoc` takes
+ * AgentHub's stage block back out of a codex lane's AGENTS.md. Plain file I/O.
  * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
  */
 
 const fs = require("node:fs");
 const path = require("node:path");
-const { git } = require("./worktree");
-
-const TEMPLATE_DIR = path.join(__dirname, "..", "..", "agents");
-const TEMPLATE_FILES = ["qc-local.md", "senior-gate-reviewer.md"];
-const EXCLUDE_LINE = ".claude/agents/";
 
 // The block older builds wrote into a codex lane's AGENTS.md. Codex lanes no
 // longer carry a pipeline, so `removeStageDoc` takes it back out.
@@ -52,54 +39,4 @@ function removeStageDoc(cwd) {
   }
 }
 
-/** The dir shared across every worktree of a repo — where info/exclude
- *  lives (same as info/attributes; MERGE_HEAD/HEAD/the index are the only
- *  per-worktree-private state, not this). */
-async function commonGitDir(cwd) {
-  const result = await git(cwd, ["rev-parse", "--git-common-dir"]);
-  const dir = result.stdout.trim();
-  return path.isAbsolute(dir) ? dir : path.join(cwd, dir);
-}
-
-/**
- * Copy both agent templates into `<lane.cwd>/.claude/agents/` (overwriting
- * any existing copy — this is a reinstall, not a merge) and idempotently
- * git-exclude that directory in the shared common git dir.
- *
- * A `codex` or `antigravity` lane gets nothing: neither CLI reads
- * `.claude/agents/`, and those lanes carry no pipeline to drive.
- *
- * @param {{cwd: string, tool?: string}} lane
- * @returns {Promise<{installed: string[]}>}
- */
-async function installAgents(lane) {
-  if (!fs.existsSync(path.join(lane.cwd, ".git"))) {
-    throw Object.assign(new Error(`lane has no .git — not a git repository: ${lane.cwd}`), {
-      code: "ENOTGITREPO",
-    });
-  }
-
-  if (lane.tool && lane.tool !== "claude") return { installed: [] };
-
-  const dest = path.join(lane.cwd, ".claude", "agents");
-  fs.mkdirSync(dest, { recursive: true });
-  const installed = [];
-  for (const name of TEMPLATE_FILES) {
-    fs.copyFileSync(path.join(TEMPLATE_DIR, name), path.join(dest, name));
-    installed.push(name);
-  }
-
-  const infoDir = path.join(await commonGitDir(lane.cwd), "info");
-  fs.mkdirSync(infoDir, { recursive: true });
-  const excludePath = path.join(infoDir, "exclude");
-  const existing = fs.existsSync(excludePath) ? fs.readFileSync(excludePath, "utf8") : "";
-  const lines = existing.split("\n").filter(Boolean);
-  if (!lines.includes(EXCLUDE_LINE)) {
-    lines.push(EXCLUDE_LINE);
-    fs.writeFileSync(excludePath, lines.join("\n") + "\n");
-  }
-
-  return { installed };
-}
-
-module.exports = { installAgents, removeStageDoc };
+module.exports = { removeStageDoc };