feat(cdp): 默认优先连接 9333 常驻 Chrome

- 无显式连接参数时先尝试 CDP 9333，失败后回退本地浏览器启动

- 修复 CDP 页选择稳定性：过滤 omnibox 系统页、无可用页时自动创建 fallback 页

- 调整页面关闭后的 active 索引维护，降低 No page found 问题

- 新增 agent-browser-stealth 二进制入口并保持与 agent-browser 行为一致

- 同步更新 CLI 帮助、README、技能文档与 docs 说明

cli/src/main.rs

@@ -513,6 +513,39 @@ fn main() {
         }
     }
 
+    // Default fork behavior: when no explicit connection mode is provided,
+    // try attaching to resident Chrome on CDP :9333 first. If unavailable,
+    // silently fall back to local launch behavior below.
+    let can_try_default_cdp = flags.cdp.is_none()
+        && !flags.auto_connect
+        && flags.provider.is_none()
+        && flags.executable_path.is_none()
+        && flags.profile.is_none()
+        && flags.state.is_none()
+        && flags.proxy.is_none()
+        && flags.args.is_none()
+        && flags.user_agent.is_none()
+        && !flags.ignore_https_errors
+        && !flags.allow_file_access
+        && flags.extensions.is_empty();
+
+    let mut launched_via_default_cdp = false;
+    if can_try_default_cdp {
+        let mut launch_cmd = json!({
+            "id": gen_id(),
+            "action": "launch",
+            "cdpPort": 9333
+        });
+
+        if let Some(ref cs) = flags.color_scheme {
+            launch_cmd["colorScheme"] = json!(cs);
+        }
+
+        if let Ok(resp) = send_command(launch_cmd, &flags.session) {
+            launched_via_default_cdp = resp.success;
+        }
+    }
+
     // Launch headed browser or configure browser options (without CDP or provider)
     if (flags.headed
         || flags.executable_path.is_some()
@@ -527,6 +560,7 @@ fn main() {
         || flags.color_scheme.is_some())
         && flags.cdp.is_none()
         && flags.provider.is_none()
+        && !launched_via_default_cdp
     {
         let mut launch_cmd = json!({
             "id": gen_id(),

cli/src/main_stealth.rs

@@ -0,0 +1 @@
+include!("main.rs");

cli/src/output.rs

@@ -2122,6 +2122,7 @@ Options:
   --headed                   Show browser window (not headless)
   --cdp <port>               Connect via CDP (Chrome DevTools Protocol)
   --auto-connect             Auto-discover and connect to running Chrome
+                             Default launch tries CDP at localhost:9333 first, then falls back to local browser launch
   --color-scheme <scheme>    Color scheme: dark, light, no-preference (or AGENT_BROWSER_COLOR_SCHEME)
   --session-name <name>      Auto-save/restore session state (cookies, localStorage)
   --config <path>            Use a custom config file (or AGENT_BROWSER_CONFIG env)