registry: add github backend for graphite - #6455

Bugbot Analysis Progress (1m 42s elapsed)

✅ Gathered PR context (2s)
✅ Analyzed code changes (1s)
✅ Completed bug detection — 0 potential bugs found (1m 38s)
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Final Result: Bugbot completed review - no issues found! ✅

Request ID: serverGenReqId_42c6519c-0864-4576-ab27-550b6e5af664