Add BrowserView.setFrame method

Adds a public BrowserView.setFrame() method for updating a view’s position and size after it has been created.

It uses the existing native resizeWebview request, keeps the local frame state in sync after a successful resize, and does not change autoResize.

Also included:

• a reusable exported BrowserViewFrame type
• unit tests for resizing, validation, removal, and native failures
• API documentation