Init agents context. Add read access logs script

[Merteg]

Summary

• Add AGENTS.md with agent instructions for this fork
• Add memory-bank/ (committed shared context for humans and agents): overview, build/test, Virtana divergence, deployment, GCP egress pricing, egress monitoring, and access-log table reference
• Add dev/read_access_logs.py and dev/READ_AL.md — script to read/inspect the access log Delta table
• Correct the access log table description: access_log_br__system is unpartitioned (matches DeltaAccessLogWriter), not partitioned by year/month/day
• Update CHANGELOG-VIRTANA.md Unreleased section accordingly