chore(ponytail-mcp): mark private, drop dead bin

ponytail-mcp reuses the repo's hooks/ via createRequire("../hooks/..."), which
reaches outside the package dir, so it can only run from a checkout (as its
README says), never as a published npm package — a publish tarball wouldn't
include ../hooks/ and would crash. The `bin` field and missing `private` made
it look publishable. Mark it private so an accidental `npm publish` can't ship
a broken package, and drop the dead bin (you point the host at ponytail-mcp/index.js).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ponytail-mcp/package.json

@@ -2,9 +2,9 @@
   "name": "ponytail-mcp",
   "version": "0.1.0",
   "description": "MCP server that serves Ponytail's lazy-senior-dev instructions as a prompt and a tool.",
+  "private": true,
   "type": "module",
   "license": "MIT",
-  "bin": { "ponytail-mcp": "./index.js" },
   "scripts": { "test": "node --test ./test/*.test.js" },
   "dependencies": {
     "@modelcontextprotocol/sdk": "^1.19.0",