docs: add npm publish badges + global-install instructions

Now that v0.4.0 / v0.5.0 / v0.6.0 are live on the npm registry, surface
that in the README:

- npm version + monthly downloads badges (zh + en READMEs)
- new "全局安装" / "Global install" snippet alongside the existing NPX
  recipe — covers users who'd rather skip the npx prefix or work offline
- CHANGELOG Unreleased entry noting the registry publish

No code changes.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

README_EN.md

@@ -9,6 +9,8 @@
 </p>
 
 <p align="center">
+  <a href="https://www.npmjs.com/package/master-skill"><img src="https://img.shields.io/npm/v/master-skill.svg?label=npm&color=cb3837" alt="npm version"></a>
+  <a href="https://www.npmjs.com/package/master-skill"><img src="https://img.shields.io/npm/dm/master-skill.svg?color=cb3837" alt="npm downloads"></a>
   <img src="https://img.shields.io/badge/License-MIT-blue.svg" alt="License: MIT">
   <img src="https://img.shields.io/badge/Python-3.9+-green.svg" alt="Python 3.9+">
   <img src="https://img.shields.io/badge/Claude%20Code-Skill-purple.svg" alt="Claude Code Skill">
@@ -125,13 +127,22 @@ This project is built out of respect for Buddhist traditions. All content is gen
 
 ### Installation
 
-**NPX (recommended)**
+**NPX (recommended, no global state)**
 
 ```bash
 npx master-skill install --all    # Install all 15 masters
 npx master-skill list             # List available masters
 ```
 
+**Global install (frequent use / offline-friendly)**
+
+```bash
+npm install -g master-skill            # Adds the binary to $PATH
+master-skill install master-zhiyi      # No more npx prefix
+master-skill list
+npm update -g master-skill             # Pull next minor / patch
+```
+
 **Claude Code**
 
 ```bash