fix: sync current x401 wire names

[creatornader]

Summary

Updates the Node SDK to match the current hosted x401 v0.2.0 wire surface from proof/x401 main.

• replaces PROOF-REQUIRED / PROOF-PRESENTATION with PROOF-REQUEST / PROOF-RESPONSE and moves verifier diagnostics to PROOF-RESULT
• replaces presentation_requirements and VP Artifact helpers with credential_requirements.digital and Result Artifact helpers
• refreshes spec fixtures, the normative ledger, README examples, and conformance mapping from proof/x401 commit 3f73cf912cd05a40bf8de3fe6c1f4bb720341336
• adds a prepare script so GitHub-pinned installs build dist before a new npm release is published

Checks

• yarn format:check
• yarn lint:check
• yarn typecheck
• yarn test
• yarn build
• yarn publint
• node scripts/extract-normative.ts