fix: make auth login selector targeting more reliable (#945)

Navigate with load, then wait for username/password/submit selectors using the default action timeout. This avoids networkidle hangs on pages with continuous background requests.

docs/src/app/commands/page.mdx

@@ -259,6 +259,8 @@ Save options:
 - `--password-selector <sel>` -- custom CSS selector for password field
 - `--submit-selector <sel>` -- custom CSS selector for submit button
 
+`auth login` navigates with `load` and then waits for the username/password/submit selectors to appear before interacting. This improves reliability on SPA login pages where fields render after initial page load.
+
 ```bash
 echo "pass" | agent-browser auth save github --url https://github.com/login --username user --password-stdin
 agent-browser auth login github

docs/src/app/security/page.mdx

@@ -47,6 +47,8 @@ agent-browser auth show github
 agent-browser auth delete github
 ```
 
+`auth login` navigates with the `load` lifecycle event and then waits for form selectors to appear before filling/clicking. This makes delayed SPA login pages more reliable while avoiding `networkidle` hangs on pages with long-lived background requests.
+
 Custom selectors can be specified if auto-detection fails:
 
 ```bash