fix(ux): silent-output, command aliases, and clearer connection errors

- output: a success response with no data payload now prints "Done" instead of
  nothing (a silent exit 0 looked like a no-op).
- commands: add top-level aliases for `get` status reads — `url`, `cdp-url`
  (and `cdp_url`), `title`, `html`, `text`, `value`, `count`, `box`, `styles`,
  `attr` — so `agent-browser url` no longer errors "Unknown command".
- connect errors now explain the Chrome 136+ realities:
  - connect-failure mentions the "Allow remote debugging?" consent dialog and
    that remote debugging is a startup flag, not a setting.
  - no-Chrome error tells the user to relaunch Chrome with
    --remote-debugging-port (auto-connect then works).
  - --cdp discovery failure explains Chrome 136+ dropped the HTTP discovery
    endpoints and to use the default auto-connect instead.

cli/src/native/cdp/discovery.rs

@@ -58,8 +58,12 @@ pub async fn discover_cdp_url_with_timeout(
     match discover_cdp_ws(host, port, timeout).await {
         Ok(ws_url) => Ok(append_query(&ws_url, query)),
         Err(ws_err) => Err(format!(
-            "All CDP discovery methods failed for {}:{}: /json/version: {}; /json/list: {}; WebSocket: {}",
-            host, port, version_err, list_err, ws_err
+            "All CDP discovery methods failed for {host}:{port}. \
+             Note: Chrome 136+ no longer serves the HTTP discovery endpoints \
+             (/json/version, /json/list), so `--cdp <port>` cannot find the target — \
+             use the default auto-connect (just `agent-browser open <url>`), which reads \
+             DevToolsActivePort and attaches over WebSocket. \
+             (details: /json/version: {version_err}; /json/list: {list_err}; WebSocket: {ws_err})"
         )),
     }
 }