fix(tools): correct HighMemoryUsage PromQL ratio (#1)

[yanyishuai]

Summary

Fixes the HighMemoryUsage alert so it compares process resident memory against machine_memory_bytes instead of dividing process_resident_memory_bytes by itself (which always evaluates to 1).

Changes

• tools/monitoring_setup.py — corrected PromQL ratio + validate_alert_rules() guard for self-dividing expressions
• tools/tests/test_monitoring_alert_exprs.py — regression coverage for recommended rules and broken expressions

Validation

python -m unittest tools.tests.test_monitoring_alert_exprs -v
python tools/monitoring_setup.py --validate
python build.py -m compliance

Dry-run alert upload behavior is unchanged aside from the corrected expression.

Closes #1

Solana wallet for bounty payout: Do4v7foHJvRJLpRRoGaVPWX6DDEjX3yTK7J91gpwUQpE

[yanyishuai]

External bounty ready for maintainer review — acceptance criteria documented in PR body. Happy to address feedback immediately.