refactor: finish the AgentHub rename and drop the MCP server

Two leftovers from the rebrand, done together because they touch the same
docs and manifests.

**Data directory.** `agent-dashboard` could not simply be renamed in the
source: it names a real directory holding the live SQLite database. Startup
now moves it once, via `migrateLegacyDataDir()` in `server/lib/claude-home.js`
— a same-filesystem rename, so it is instant even at multiple gigabytes and
cannot leave two divergent copies. `getDataDir()` stays PURE and resolves to
the legacy path until the move happens; the first version of this put the
rename inside the getter, which meant `npm run test:server` relocated the
developer's real database as a side effect. The call sits behind
`require.main === module` and ahead of the router requires, because those pull
in db.js, which opens SQLite at module load. A failed rename is silent and the
old directory keeps being used: an unfashionable directory name beats a blank
database beside an unreachable one. Same treatment for the port-discovery file
(`.agent-dashboard.json` → `.agenthub.json`, old one dropped on write).

Not renamed on purpose: the Sagi localStorage keys (renaming silently resets
everyone's prefs) and the PWA manifest `id` (changing it orphans an installed
app).

**MCP server.** 4 tool calls in 46 days across 577,132 events, against 4,556
lines of TypeScript, a 2 MB committed build artifact, and a pre-commit guard
that had already blocked commits twice. Deleted: `mcp/`, the maintainer skills
and `mcp-reviewer` agent, the build check, `plugins/agenthub/.mcp.json`,
`docs/MCP.md`, 12 npm scripts, 5 Makefile targets, and every doc section
describing it.

Kept, because they are unrelated things sharing the name: the Config
Explorer's MCP tab and its API, per-lane Playwright MCP, the agenthub-config
plugin's MCP audit, and the historical `mcp__plugin_agenthub_*` events that
analytics must keep attributing.

Verified: server 1432/1432, client 459/459, tsc clean, prettier clean. Both
directions of the migration proven — a sandbox-HOME test run leaves the legacy
directory untouched, and a real boot moves it with its contents intact.

package.json

@@ -1,5 +1,5 @@
 {
-  "name": "agent-dashboard",
+  "name": "agenthub",
   "version": "1.4.6",
   "bin": {
     "agenthub": "bin/agenthub.js"
@@ -12,7 +12,6 @@
     "server",
     "scripts",
     "data",
-    "mcp",
     "statusline",
     "README.md"
   ],
@@ -35,8 +34,6 @@
     "real-time",
     "monitoring",
     "activity-tracking",
-    "mcp",
-    "model-context-protocol",
     "nodejs",
     "express",
     "react",
@@ -60,18 +57,6 @@
     "start": "node server/index.js",
     "setup": "npm install && (cd client && npm install) && (cd vscode-extension && npm install) && npm run link-cli",
     "update:pull-setup": "git pull --ff-only && npm run setup",
-    "mcp:install": "npm --prefix mcp install",
-    "mcp:check-build": "node scripts/check-mcp-build.js",
-    "mcp:build": "npm --prefix mcp run build && node scripts/check-mcp-build.js --write",
-    "mcp:start": "npm --prefix mcp run start",
-    "mcp:start:http": "npm --prefix mcp run start:http",
-    "mcp:start:repl": "npm --prefix mcp run start:repl",
-    "mcp:dev": "npm --prefix mcp run dev",
-    "mcp:dev:http": "npm --prefix mcp run dev:http",
-    "mcp:dev:repl": "npm --prefix mcp run dev:repl",
-    "mcp:typecheck": "npm --prefix mcp run typecheck",
-    "mcp:docker:build": "docker build -f mcp/Dockerfile -t agent-dashboard-mcp:local .",
-    "mcp:podman:build": "podman build -f mcp/Dockerfile -t localhost/agent-dashboard-mcp:local .",
     "install-hooks": "node scripts/install-hooks.js",
     "seed": "node scripts/seed.js",
     "import-history": "node scripts/import-history.js",
@@ -80,7 +65,6 @@
     "test": "node --test server/__tests__/*.test.js && cd client && npm test",
     "test:server": "node --test server/__tests__/*.test.js",
     "test:client": "cd client && npm test",
-    "test:mcp": "npm --prefix mcp run test",
     "format": "prettier --write .",
     "format:check": "prettier --check .",
     "openapi:yaml": "node scripts/generate-openapi-yaml.js",