Refine evidence-driven skill execution guidance

[shinpr]

Summary

• make English pure skills more self-contained with repository-backed prerequisite detection and explicit phase, completion, and escalation evidence
• align task sizing, bounded verification, test-boundary selection, and cross-skill execution rules
• mirror the changes into natural Japanese and release them as version 1.25.4

Validation

• npm run check:skills-index
• npm run build
• npm test -- --passWithNoTests