Module validator 

PhysicalPlanValidator: structural and binding-dependent validation.

Two-tier validation:

1. Structural validation (no bindings required): runs once before cache-write. Checks ID uniqueness, fragment DAG integrity, operator input/output consistency, property derivation, capability requirements, memory policy, and root output contract.
2. Binding-dependent validation (requires parameter values, auth): runs at instantiation time. Re-checks compatibility, parameter frame, transaction mode, and runtime limits.

Structs

PhysicalPlanValidator

Validates a PhysicalPlan for correctness and consistency.

ValidationResult

Result of a validation pass, collecting all errors instead of failing fast.

Enums

ValidationTier

The two validation tiers.