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.

scripts/expand-ts-module-docs.py

@@ -2,7 +2,7 @@
 """
 expand-ts-module-docs.py — append rich TSDoc blocks to TypeScript modules (comments only).
 
-Used to deepen in-file documentation for client, MCP, and desktop packages without
+Used to deepen in-file documentation for the client and desktop packages without
 changing runtime behavior. Idempotent: skips files that already contain MODULE_GUIDE.
 
 @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
@@ -53,11 +53,6 @@ def topic_blurb(path: Path) -> str:
             "Route-level screen mounted by `App.tsx`; fetches scoped REST data, subscribes "
             "to WebSocket deltas via `eventBus`, and renders inside `Layout`."
         )
-    if path.parts[0:2] == ("mcp", "src"):
-        hints.append(
-            "Part of the local MCP server (`npm run mcp:start`) that exposes dashboard "
-            "operations as MCP tools for Claude Code and other hosts."
-        )
     if path.parts[0:2] == ("desktop", "src"):
         hints.append(
             "Electron main/preload process code for the packaged desktop app — embeds the "
@@ -99,7 +94,7 @@ def topic_blurb(path: Path) -> str:
         )
     if not hints:
         hints.append(
-            "Dashboard module consumed by the React client, MCP tools, or desktop shell "
+            "Dashboard module consumed by the React client or the desktop shell "
             "depending on deployment mode."
         )
     return " ".join(hints)
@@ -170,7 +165,6 @@ def build_guide(path: Path, source: str) -> str:
             " * ## Testing pointers",
             " * - Prefer colocated `__tests__` with Vitest + Testing Library for UI.",
             " * - Server contract changes require `npm run test:server` and OpenAPI sync.",
-            " * - MCP edits: `npm run mcp:typecheck` and `npm run mcp:build`.",
             " *",
             " * ## Related docs",
             " * - `ARCHITECTURE.md` — hooks → API → SQLite → WebSocket → UI pipeline.",