Release v0.3.11: position repo as Grok plugin with clearer install

Document plugin-first packaging (manifest, commands, skills, hooks) and
have install.sh build the CLI, install the tmux dashboard, and register
the plugin so clone-and-setup matches how the project is shipped.

plugin.json

@@ -1,7 +1,7 @@
 {
   "name": "grok-build-hud",
-  "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）",
+  "version": "0.3.11",
+  "description": "Grok Build 插件：同窗口实时状态条（上下文、配额、入出缓存 token、工具与待办）；tmux 多行 HUD + 会话斜杠命令",
   "author": {
     "name": "Redredchen01"
   },