Fix HighMemoryUsage alert ratio expression

[natchapolwu]

Summary

Fixes the HighMemoryUsage Prometheus alert so it compares resident memory to total machine memory instead of dividing process_resident_memory_bytes by itself.

/claim #1

Changes

• Replaced the self-dividing HighMemoryUsage expression with process_resident_memory_bytes / machine_memory_bytes > 0.9.
• Added find_self_dividing_alerts() to reject alert rules where the same metric appears on both sides of /.
• Added unit tests for the recommended alert rules and the self-division guard.
• Made alert upload/init return a failure code if validation rejects a rule.

Testing

• python -m unittest tools.test_monitoring_setup
• python tools\monitoring_setup.py --alerts --dry-run
• python -m py_compile tools\monitoring_setup.py tools\test_monitoring_setup.py

Checklist

• Relevant modules affected by these changes build locally
• Tests pass locally
• Diagnostic build log is committed in this PR
• Documentation has been updated, if applicable
• Configuration or schema changes are documented, if applicable
• No generated build artifacts are committed, except the required diagnostic build log
• Changes are scoped to the PR purpose and avoid unrelated cleanup
• Security, privacy, and error-handling implications have been considered

Notes

The repository PR template asks for a diagnostic build log. This change is a Python-only monitoring script fix, and the available local verification is the unittest/dry-run/py_compile sequence above. No full diagnostic build was run.