Introduce the conformance-profile validation API

[juherr]

Goal

Provide a reusable API for business-profile validation beyond XSD correctness.

Scope

• Introduce ConformanceProfile.
• Introduce immutable ConformanceResult.
• Define messages with stable code, severity, and business path.
• Compose schema validation and profile validation without conflating them.
• Define profile identity and versioning.

Acceptance criteria

• Profiles can validate generated model objects.
• Results contain stable machine-readable codes.
• Every diagnostic has severity and a useful business path.
• Multiple profiles can be composed deterministically.
• API behavior is documented with custom-profile examples.

Planning

• Priority: P1
• Complexity: L