feat!: bump to v7 for liveness probes breaking changes

BREAKING CHANGE: Schema version bumped to "2" with new schema/v2/ directory.
The health_check field is deprecated in favor of probes.readiness. The verify
field is renamed to skip_if. Progress event JSON keys renamed from
health_check_* to readiness_probe_*. State field health_phases renamed to
readiness_phases.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: peter-adam-dy