review and agree on CLAUDE.md

[dangrondahl]

The `CLAUDE.md` file instructs Claude Code how to work in this repo. It should
be reviewed and expanded to cover conventions the whole team agrees on.

Topics to cover

• Conventional Commits as the required commit/PR title format
• Diátaxis framework as the writing guide for new documentation
  (https://diataxis.fr/)
• Vale integration for prose linting (once set up)
• Any other agent behaviour preferences (e.g. never auto-push, always ask before
  creating issues)

Tasks

• Review current `CLAUDE.md` with the team
• Add agreed conventions and guidelines
• Link to relevant external references (Diátaxis, Vale, Conventional Commits)