Make Chinese README primary; ship English as README.en.md

Restructure docs so README.md is full Chinese documentation with TOC.
English content moves to README.en.md; drop README.zh-CN.md. Align
CONTRIBUTING, install script, package/plugin descriptions, and skill links.

plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "grok-build-hud",
-  "version": "0.3.9",
-  "description": "Live multi-line status strip for Grok Build: context, quota, tokens, tools, todos, git",
+  "version": "0.3.10",
+  "description": "Grok Build 实时状态条：上下文、配额、token、工具、待办（同窗口 tmux）",
   "author": {
     "name": "Redredchen01"
   },