[minor] Require first-customer release tuple

[libops-agent]

Summary

• promote the platform manifest contract to schema v2 for the first-customer release
• require all 17 API/controller/runner/Vault/edge/Task Agent images with immutable source and attestations
• bind Terraform and the canonical skills bundle to exact commits and require the embedded manifest digest
• require named hosted onboarding, GitHub, Slack, Vault, edge, Task Agent, MariaDB, and rollback evidence
• resolve every platform component to an accountable owner and reject incomplete tuples

Validation

• go test ./ci/github -run PlatformRelease -count=1
• GNUPGHOME=/tmp/libops-dotgithub-gnupg go test ./...
• actionlint
• direct v2 manifest validator
• JSON syntax and git diff --check