Add scaffold tool for creating new health checks [2/2]

[gustcol]

Summary

Ref: #75
Depends on: #77

• Introduce bin/create_new_health_check.py, a scaffold tool that automates the creation of new health checks by generating all required files and registering the check across all touchpoints
• Generated checks use the HealthCheckRuntime context manager from Add HealthCheckRuntime context manager for shared boilerplate [1/2] #77
• Supports --group flag for grouped checks (@click.group()) and --dry-run for previewing changes
• Idempotent — safe to re-run without duplicating entries
• Updates the "Adding New Health Check" documentation with a Quick Start section

Stacked PR series: [1/2] Runtime helper (#77) → [2/2] Scaffold tool (this PR)

What the tool does

$ python bin/create_new_health_check.py check_ntp_sync --dry-run
[dry-run] Would create: gcm/health_checks/checks/check_ntp_sync.py
[dry-run] Would create: gcm/tests/health_checks_tests/test_check_ntp_sync.py
[dry-run] Would create: website/docs/GCM_Health_Checks/health_checks/check-ntp-sync.md
[dry-run] Would add import to gcm/health_checks/checks/__init__.py
[dry-run] Would add __all__ entry to gcm/health_checks/checks/__init__.py
[dry-run] Would add checks.check_ntp_sync to gcm/health_checks/cli/health_checks.py
[dry-run] Would add CHECK_NTP_SYNC to gcm/schemas/health_check/health_check_name.py
[dry-run] Would add disable_check_ntp_sync to gcm/monitoring/features/.../health_checks_features.py

Action	Target	Insert Order
Create	gcm/health_checks/checks/check_{name}.py	—
Create	gcm/tests/health_checks_tests/test_check_{name}.py	—
Create	website/docs/.../check-{name}.md	—
Modify	checks/__init__.py	Alphabetical import + append __all__
Modify	cli/health_checks.py	Append to list_of_checks
Modify	health_check_name.py	Alphabetical enum entry
Modify	health_checks_features.py	Alphabetical disable_ field

Test plan

• nox -s tests -- gcm/tests/test_create_health_check.py — 15 tests covering validation, file generation, registration, idempotency, dry-run, grouped checks
• python bin/create_new_health_check.py check_test_example --dry-run — integration smoke test
• nox -s lint
• nox -s format
• Verify Docusaurus website builds with updated docs

[github-actions]

CI Commands

The following CI workflows run automatically on every push and pull request:

Workflow	What it runs
GPU Cluster Monitoring Python CI	lint, tests, typecheck, format, deb build, pyoxidizer builds
Go packages CI	shelper tests, format, lint

---

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Command	Description	Requires approval?
/metaci tests	Runs Meta internal integration tests (pytest)	Yes — a maintainer must trigger the command and approve the deployment request
/metaci integration tests	Same as above (alias)	Yes

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[luccabb]

run these from create_new_health_check.py?

[gustcol]

Good idea — the scaffold tool now runs generate_features.py and ufmt format gcm automatically as a post-scaffold step (skipped in --dry-run mode). Updated the docs to remove the manual instructions.