Sign() computes signature over canonical YAML (excluding sign field),
Verify() checks against public key. Tampered manifests are rejected.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Manifest struct, Permissions, Parse() from YAML, SlotNames() helper.
Foundation for Phase 4 module system.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>