Improve skill execution guidance and consistency

[shinpr]

Summary

• Remove redundant baseline explanations and examples while preserving repository-specific execution rules.
• Align verification levels, testing boundaries, scope handling, and review status semantics across skills and agents.
• Clarify E2E value scoring and update the package version to 0.9.2.

Validation

• npm run check:skills-index
• npm test
• TOML syntax validation for modified agent definitions
• git diff --check