feat: 新增 setup-opencode action，支持 npm 全局安装和智能缓存

- 使用 npm 全局安装 OpenCode，支持版本管理和自动更新
- 智能缓存策略：缓存 npm 目录和全局安装，加速后续构建
- 支持淘宝镜像源和自定义 npm 镜像，国内环境友好
- 版本检测：自动比对已安装版本，避免重复安装
- 输出安装版本、缓存命中状态和更新状态
- 提供详细的使用文档和多场景示例

setup-opencode/examples/basic-usage.yml

@@ -0,0 +1,36 @@
+name: Basic OpenCode Usage
+
+on:
+  push:
+    branches: [ main, develop ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: 检出代码
+        uses: actions/checkout@v4
+
+      - name: 安装 OpenCode
+        id: setup-opencode
+        uses: ./.gitea/actions/setup-opencode
+        with:
+          version: 'latest'
+
+      - name: 显示安装信息
+        run: |
+          echo "OpenCode 版本: ${{ steps.setup-opencode.outputs.version }}"
+          echo "缓存命中: ${{ steps.setup-opencode.outputs.cache-hit }}"
+          echo "执行更新: ${{ steps.setup-opencode.outputs.updated }}"
+
+      - name: 验证安装
+        run: |
+          opencode --version
+          which opencode
+
+      - name: 使用 OpenCode
+        run: |
+          opencode build

setup-opencode/examples/china-mirror.yml

@@ -0,0 +1,33 @@
+name: China Mirror Example
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: 检出代码
+        uses: actions/checkout@v4
+
+      - name: 安装 OpenCode（淘宝镜像）
+        id: setup
+        uses: ./.gitea/actions/setup-opencode
+        with:
+          version: 'latest'
+          use-taobao-registry: 'true'
+
+      - name: 显示安装信息
+        run: |
+          echo "安装版本: ${{ steps.setup.outputs.version }}"
+          echo "缓存命中: ${{ steps.setup.outputs.cache-hit }}"
+          
+          if [[ "${{ steps.setup.outputs.cache-hit }}" == "true" ]]; then
+            echo "✅ 使用缓存，快速完成安装"
+          else
+            echo "📥 通过 npm 安装完成"
+          fi
+
+      - name: 构建项目
+        run: |
+          opencode build --release

setup-opencode/examples/custom-registry.yml

@@ -0,0 +1,21 @@
+name: Custom Registry Example
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: 检出代码
+        uses: actions/checkout@v4
+
+      - name: 使用自定义 npm 镜像源
+        uses: ./.gitea/actions/setup-opencode
+        with:
+          version: '1.2.3'
+          npm-registry: 'https://registry.npmmirror.com'
+
+      - name: 构建
+        run: |
+          opencode build

setup-opencode/examples/specific-version.yml

@@ -0,0 +1,21 @@
+name: Specific Version Example
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    
+    steps:
+      - name: 检出代码
+        uses: actions/checkout@v4
+
+      - name: 安装 OpenCode 1.2.3
+        uses: ./.gitea/actions/setup-opencode
+        with:
+          version: '1.2.3'
+          cache-prefix: 'opencode-stable'
+
+      - name: 构建项目
+        run: |
+          opencode build --release