feat: add creative writing skill

[tongshu2023]

Summary

• add a new 02-creative-writing skill built around a practice-first write -> reflect -> revise loop
• cover story structure, character development, writing craft, genre exploration, and revision workflows
• wire the new skill into the tree between 02-humanities-social-tutor and 03-academic-writing

Verification

• Python structure check confirmed the new skill contains the required six sections
• Python tree check confirmed the new skill directory exists and the requested edges were added
• npm run parse-skills could not complete because dependencies are not installed and npx failed while trying to fetch tsx
• npm run lint could not complete because eslint was not available in the workspace

Closes #10