Add curated latex-paper skill

[0xNoramiya]

Summary

• add a new curated skill: skills/.curated/latex-paper
• include LaTeX paper scaffolding templates (article, ieeetran, acmart)
• include reusable scripts for scaffold, compile, lint, ref/citation checks, and tex-to-pdf conversion
• include references and snippet assets for research writing workflows

Notes

• skill frontmatter and metadata validated with quick_validate
• scripts pass shell syntax checks
• no external runtime deps beyond common LaTeX tooling (latexmk, optional chktex)