Amp adds GitHub webhook support for PR comments, reviews, and CI results

Amp now follows up on the GitHub pull requests it opens, routing comments, reviews, and CI results into the same thread. The new first-class GitHub Webhooks integration lets an agent subscribe to events or spawn a new orb for each new issue or PR, optionally filtered by label. Users manage these subscriptions in Settings under MCP & Integrations, where they can edit or pause them.