Update the GitHub integration page to lead with the native integration

[patrikbraborec]

Context

The build-on-push section of the GitHub integration page tells the reader to copy the Build Actor API endpoint and add a webhook in the repository settings. That is the manual route, not automatic builds on a Git-linked Actor, so a reader following the page builds their own pipeline instead of using the integration. An AI agent did exactly that: it wrote its own GitHub Actions workflow yaml.

To do

• Lead the build section with automatic builds on a Git-linked Actor.
• Keep the webhook route as a fallback, and say which cases still need it.
• Check the rest of the page against the current Console flow: screen names, settings paths, and the private repository step.

Done when

The default path on the page is the native integration, and every step matches Console.