Add binding_hash conformance vectors

[Math1987]

Summary

• add seven byte-identical known-answer vectors for the Access Request Approval binding_hash construction
• cover single-item and bulk inputs, subject.properties.act removal, binding_context_members selection, absent versus null, JCS number serialization, and array/item ordering
• add a dependency-free Node verifier and a Make target
• link the non-normative vector corpus from the Binding Token Integrity section

Closes #556

Validation

• node profiles/authzen-access-request-approval/test-vectors/verify-binding-hash-vectors.mjs
• make -C profiles/authzen-access-request-approval test-vectors
• byte comparison against canonicalize@3.0.0
• independent Python comparison of canonical bytes, SHA-256 hex, and unpadded base64url digests
• git diff --check

IPR

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[Math1987]

Hi @alexolivier,

I’m following up on these binding_hash conformance vectors for the Access Request and Approval Profile. The PR remains limited to informational vectors, a dependency free verifier, and the related documentation link. I would be glad to make any changes needed for review.

[alexolivier]

Hey, thanks for the additions. We don't really have a precedent of having these scripts being referenced from a spec before. So I'm not sure how we approach this, given we don't want a published spec to point at something that can move if it just sits in a Git repo.