fix: 修复 QQ Bot 配置后 Gateway 无法启动的问题

1. 清除旧版 "agent" 废弃键 — 保存 channel 配置时自动删除旧的 agent 键，
   防止 OpenClaw 报 "agent.* was moved" 错误（前端 + 服务端双重防御）
2. Dashboard URL 动态端口探测 — 将硬编码 18789 改为扫描 18789-18799，
   解决端口被占用时打不开 Dashboard 的问题
3. 安装脚本配置格式升级 — install.sh / install.ps1 / install-silent.ps1
   生成的 openclaw.json 从旧的 "agent" 格式迁移到 "agents.defaults.model.primary"
4. 文档示例同步更新 — CLAUDE.md / cloud.html / guide.html 中的配置示例

影响文件: 14 个（portable/, install/, website/, u-claw-app/, usb-release/）

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

website/install-silent.ps1

@@ -198,31 +198,46 @@ if ($SkipConfig) {
     }
 
     if ($resolvedProvider -eq "custom" -and $resolvedBaseUrl) {
+        $pName = "custom"
         $configJson = @"
 {
   "gateway": {
     "mode": "local",
     "auth": { "token": "uclaw" }
   },
-  "agent": {
-    "model": "$resolvedModel",
-    "apiKey": "$ApiKey",
-    "baseUrl": "$resolvedBaseUrl"
-  }
+  "models": {
+    "mode": "merge",
+    "providers": {
+      "$pName": {
+        "baseUrl": "$resolvedBaseUrl",
+        "apiKey": "$ApiKey",
+        "api": "openai-completions",
+        "models": [{ "id": "$resolvedModel" }]
+      }
+    }
+  },
+  "agents": { "defaults": { "model": { "primary": "$pName/$resolvedModel" } } }
 }
 "@
     } else {
+        $pName = $resolvedProvider
         $configJson = @"
 {
   "gateway": {
     "mode": "local",
     "auth": { "token": "uclaw" }
   },
-  "agent": {
-    "model": "$resolvedModel",
-    "apiKey": "$ApiKey",
-    "provider": "$resolvedProvider"
-  }
+  "models": {
+    "mode": "merge",
+    "providers": {
+      "$pName": {
+        "apiKey": "$ApiKey",
+        "api": "$(if ($pName -eq 'anthropic') {'anthropic'} else {'openai-completions'})",
+        "models": [{ "id": "$resolvedModel" }]
+      }
+    }
+  },
+  "agents": { "defaults": { "model": { "primary": "$pName/$resolvedModel" } } }
 }
 "@
     }