GitHub API rate limit from shared token

Your CI/CD platform integrates with the GitHub API to fetch repos, check statuses, and post comments. At 14:00 builds start stalling and PR status checks stop updating. Dashboards: GitHub API responses shift to HTTP 403 with 'API rate limit exceeded' and 'You have exceeded a secondary rate limit'; the X-RateLimit-Remaining header is at 0; your fleet shares a single GitHub App installation token across all customers' builds. Recent context: you onboarded several large enterprise customers this week, multiplying concurrent builds; nothing else changed. How do you triage and mitigate?