Core capacity, setup, and billing preview updates

Core capacity handling, GitHub App setup guidance, and signed-out billing preview updates are now available.

• For eligible capacity waits where Runzivo confirms the job never started and no runner resources remain allocated, Runzivo waits up to 900 seconds by default. This platform limit is configurable. When the wait expires, Runzivo ends the local attempt with zero execution charge, alerts staff, and provides rerun guidance. The attempt does not cancel the GitHub workflow or its sibling jobs.
• After installation, setup checks the current GitHub App permissions again instead of relying on a stale cached mismatch. Onboarding explains each requested permission and identifies AI-write permissions as Early Access permissions.
• The signed-out billing preview labels example checkout data as a preview. It does not indicate that checkout is available.