CI: Topology discovery validation tests

[renecannao]

Summary

Current smoke tests only verify API endpoints return HTTP 200. We need tests that validate orchestrator correctly discovers and represents the actual replication topology.

Proposed Tests

• Verify discovered cluster has correct number of instances (3)
• Verify master is identified correctly (read_only=0, no master key)
• Verify replicas are identified correctly (read_only=1, correct master key)
• Verify GTID positions are being read
• Verify replication lag is being measured (Seconds_Behind_Master)
• Verify uptime and last-checked timestamps are recent
• Verify cluster alias detection works (DetectClusterAliasQuery)
• Compare orchestrator's view of topology against direct MySQL queries

Acceptance Criteria

• Tests validate topology state, not just HTTP status codes
• Tests cross-reference orchestrator API data with direct MySQL queries
• Tests integrated into CI workflow

[coderabbitai]

🔗 Related PRs

#51 - Add functional test CI: Docker MySQL topology + ProxySQL + failover tests [merged]

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