Exclude CLAUDE.md from website rendering

[3keyroman]

pkic.org mounts this repository as Hugo content, so CLAUDE.md was published as a page at https://pkic.org/wg/pkimm/model/claude/ with an empty page title, and the model section navigation linked to it.

This adds Hugo build front matter to CLAUDE.md so the file stays in the repository without being published:

build:
  render: never
  list: never

The same block is already used by categories/templates/_index.md and release-notes/templates/_index.md, and both of those pages return 404.

A bullet in Authoring conventions records why the block is there, so it is not later removed as stray front matter.

Refs #47

[vanbroup]

Maybe we should simply add these files to the ignore files config in Hugo?

[3keyroman]

Maybe we should simply add these files to the ignore files config in Hugo?

Agree, this should be another safeguard, I will also open PR to site to add it to ignore list.

[vanbroup]

# Ignore all hidden files/folders and AI instruction files from static site generation
ignoreFiles:
  - "(^|/)\\."                           # Matches ANY hidden folder or hidden file (.github/, .ai/, .env, .cursorrules)
  - "(AGENTS|CLAUDE|COPILOT|PROMPTS)\\.md$" # Matches non-hidden markdown instructions anywhere