Validate Salesforce metadata before deploying. TRIGGER when the user asks to validate a deploy, do a dry-run, check before deploying, or targets a Production org for any deploy operation. Routes prod targets to `sf project deploy validate` (returns a 10-day quick-deploy job ID) and sandbox/scratch targets to `sf project deploy start --dry-run`. DO NOT TRIGGER for actual deploys (use platform-metadata-deploy) or destructive changes (use platform-destructive-deploy).
