feat(blueprint): add purpose-indexed validator interfaces

[satran004]

Summary

• publish one correlated CIP-57 entry per supported explicit multi-validator purpose
• bind artifact and verification selection to the exact title and purpose
• map CERTIFY to the standard CIP-57 publish purpose, following Aiken; keep VOTE and PROPOSE fail-closed
• add real cardano-client-lib compatibility coverage, migration diagnostics, docs, and P.4 evidence

Verification

• 2,198 tests across nine affected modules, zero failures
• verification/p4/scripts/verify.sh
• docs npm run build
• git diff --check

Risk and compatibility

• Stacked on feat(compiler): enforce strict on-chain data boundaries #83; merge only after its strict-boundary prerequisite and the earlier verification stack.
• Existing single-purpose script bytes remain unchanged, but regenerated blueprint JSON gains explicit purpose metadata.
• Explicit supported-purpose @MultiValidator titles become purpose-qualified, requiring artifact consumers to select the exact interface.
• CERTIFY is represented as CIP-57 publish. VOTE and PROPOSE cannot be represented truthfully by the pinned CIP-57 vocabulary and fail with documented --no-blueprint guidance.
• Legacy purpose-free blueprints fail with an actionable rebuild diagnostic rather than selecting an ambiguous interface.

Dependency

Depends on #83.