Organize security-audit skill into standard subdirectories (references, scripts, resources)

[kamusis]

Hi team, thanks for open-sourcing this skill!

Currently all 20 files in skills/security-audit/ are flat in the root directory. Following common Agent Skill conventions (e.g. Anthropic's skill spec), it would be much cleaner to group auxiliary files into standard subdirectories:

skills/security-audit/
├── SKILL.md
├── references/      # 14 companion & methodology docs (*.md)
├── resources/       # report-schema.json
└── scripts/         # validator scripts & tests (*.cjs)

Main benefits:

• Better context loading: Keeps SKILL.md as the lightweight entry point so agents/runtimes only pull in domain companions on-demand rather than ingesting all docs upfront.
• Tooling compatibility: Plays nicely with skill loaders and platforms that expect executable code in scripts/ and reference material in references/.

Happy to open a PR for this with updated relative paths and passing tests if you're open to the change.