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>

install/install.ps1

@@ -520,31 +520,46 @@ if ($hasConfig) {
 
     # Write config
     if ($cfg.provider -eq "custom" -and $cfg.baseUrl) {
+        $providerName = "custom"
         $configJson = @"
 {
   "gateway": {
     "mode": "local",
     "auth": { "token": "uclaw" }
   },
-  "agent": {
-    "model": "$($cfg.model)",
-    "apiKey": "$apiKey",
-    "baseUrl": "$($cfg.baseUrl)"
-  }
+  "models": {
+    "mode": "merge",
+    "providers": {
+      "$providerName": {
+        "baseUrl": "$($cfg.baseUrl)",
+        "apiKey": "$apiKey",
+        "api": "openai-completions",
+        "models": [{ "id": "$($cfg.model)" }]
+      }
+    }
+  },
+  "agents": { "defaults": { "model": { "primary": "$providerName/$($cfg.model)" } } }
 }
 "@
     } else {
+        $providerName = $cfg.provider
         $configJson = @"
 {
   "gateway": {
     "mode": "local",
     "auth": { "token": "uclaw" }
   },
-  "agent": {
-    "model": "$($cfg.model)",
-    "apiKey": "$apiKey",
-    "provider": "$($cfg.provider)"
-  }
+  "models": {
+    "mode": "merge",
+    "providers": {
+      "$providerName": {
+        "apiKey": "$apiKey",
+        "api": "$(if ($providerName -eq 'anthropic') {'anthropic'} else {'openai-completions'})",
+        "models": [{ "id": "$($cfg.model)" }]
+      }
+    }
+  },
+  "agents": { "defaults": { "model": { "primary": "$providerName/$($cfg.model)" } } }
 }
 "@
     }