feat: add multi-platform plugin support and session-start hook

Add support for 5 platforms beyond NPX:

- Claude Code: .claude-plugin/plugin.json + marketplace.json
- Cursor: .cursor-plugin/plugin.json + hooks-cursor.json
- Codex CLI: .codex/INSTALL.md with symlink setup
- OpenCode: .opencode/INSTALL.md with plugin config
- Gemini CLI: gemini-extension.json + GEMINI.md

Infrastructure:
- SessionStart hook with platform detection (Claude Code,
  Cursor, Copilot CLI) that injects available masters list
- Cross-platform run-hook.cmd polyglot wrapper (Windows + Unix)
- .version-bump.json for unified version management across
  all platform config files
- Update README/README_EN with multi-platform install instructions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

README.md

@@ -88,24 +88,41 @@ npx master-skill install --all
 npx master-skill list
 ```
 
-**Claude Code**
+**Claude Code（插件方式）**
 
 ```bash
+# 即将上线插件市场，目前使用手动安装：
 git clone https://github.com/xr843/Master-skill ~/Master-skill
 cd ~/Master-skill && pip install -r requirements.txt
 for d in prebuilt/*/; do ln -sf "$(pwd)/$d" ~/.claude/skills/"$(basename $d)"; done
 ln -sf "$(pwd)" ~/.claude/skills/create-master
 ```
 
-**Codex CLI**
+**Cursor**
 
 ```bash
 git clone https://github.com/xr843/Master-skill ~/Master-skill
-cd ~/Master-skill && pip install -r requirements.txt
-for d in prebuilt/*/; do ln -sf "$(pwd)/$d" ~/.codex/skills/"$(basename $d)"; done
-ln -sf "$(pwd)" ~/.codex/skills/create-master
+# Cursor 自动检测 .cursor-plugin/plugin.json 并注册技能
 ```
 
+**OpenCode**
+
+在 `opencode.json` 中添加：
+
+```json
+{
+  "plugin": ["master-skill@git+https://github.com/xr843/Master-skill.git"]
+}
+```
+
+**Codex CLI**
+
+参见 [.codex/INSTALL.md](.codex/INSTALL.md)
+
+**Gemini CLI**
+
+本项目包含 `gemini-extension.json` 和 `GEMINI.md`，Gemini CLI 自动发现并加载。
+
 ### 使用预置法师
 
 在支持 AgentSkills 的环境（Claude Code / Codex CLI / OpenClaw）中直接调用：