The bridge to agent-scale Git infrastructure

This post details the immediate bridge to agent-scale Git infrastructure by migrating the busiest repositories to Azure. It introduces a change to the quorum's write serialization from repository-wide to per-reference, which significantly increases write throughput and reduces latency by allowing concurrent writes to different references. This change is crucial for migrating the remaining repositories to Azure. Furthermore, it outlines the next step of decoupling storage from compute by introducing virtual replicas that serve reads from Azure Blob Storage, enabling independent scaling of read traffic.