feat(extension): add open-user-tab support

[sangnt1552314]

Description

Adds support for opening a new tab in an existing Chrome window instead of only using the dedicated automation window.

Changes

• Add open-user-tab operation to the extension protocol
• Implement extension handling to find a non-automation Chrome window and open a tab there
• Add openUserTab() to the browser page interface and implementation
• Add open-user-tab as a pipeline step
• Mark the step as browser-only for capability routing

Why

Some commands should open content for the user in their normal Chrome window without being closed by the automation window lifecycle.

Testing

• Reload the browser extension after building
• Run a command that uses open-user-tab
• Verify the URL opens as a new tab in an existing Chrome window
• Verify the automation window behavior remains unchanged for normal browser actions