Refine review scope contracts and remove unsupported defaults

[shinpr]

Summary

• Replace the frozen review change-set contract with implementation-artifact scope that is refreshed before each review pass.
• Remove unused verifier inputs, rigid repository-scope fallbacks, unreachable task-file checks, and unsupported prompt defaults.
• Keep accessibility standards tied to accepted governing sources and bump all plugin manifests to 0.24.6.

Validation

• git diff --check
• pnpm sync:check
• pnpm check:skills-index
• claude plugin validate .
• claude plugin validate dev-workflows
• claude plugin validate dev-workflows-frontend
• claude plugin validate dev-workflows-fullstack
• claude plugin validate dev-skills