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

docs/src/app/cdp-mode/page.mdx

@@ -6,6 +6,8 @@ export const metadata = pageMetadata("cdp-mode")
 
 Connect to an existing browser via Chrome DevTools Protocol:
 
+Default behavior in this fork: when `--cdp` is omitted, agent-browser first tries `localhost:9333` and falls back to local browser launch if CDP is unavailable.
+
 ```bash
 # Start Chrome with: google-chrome --remote-debugging-port=9222
 
@@ -52,7 +54,7 @@ AGENT_BROWSER_AUTO_CONNECT=1 agent-browser snapshot
 Auto-connect discovers Chrome by:
 
 1. Reading Chrome's `DevToolsActivePort` file from the default user data directory
-2. Falling back to probing common debugging ports (9222, 9229)
+2. Falling back to probing common debugging ports (9222, 9229, 9333)
 
 This is useful when:
 

docs/src/app/configuration/page.mdx

@@ -6,6 +6,8 @@ export const metadata = pageMetadata("configuration")
 
 Create an `agent-browser.json` file to set persistent defaults instead of repeating flags on every command.
 
+In this fork, default launch behavior already prefers a resident Chrome at `localhost:9333` (CDP) and falls back to local Playwright launch when unavailable.
+
 ## Config File Locations
 
 agent-browser checks two locations, merged in priority order: