Add brand guidelines skill for general-purpose agents

[JorimTheuns]

Adds skills/brand-guidelines.md: an agent-facing brand reference distilled from six months of working corrections, written for any general-purpose dembrane helper agent.

What's in it

• The name: lowercase dembrane everywhere, never bolded; ECHO is legacy
• Voice: grounded/human/approachable, "language model" not "AI", en-UK spelling
• Hard-learned phrasing rules (the things agents get wrong by default):
  • em dashes are an AI tell: one per document max, aim for zero
  • no violent or martial metaphors, with working replacements
  • Dutch is je/jij never u/uw, stressed jouw for emphasised ownership
• Positioning boundaries: claims stop at the record, "holds up under pressure" belongs to the participant, no "incorruptible" in copy, position-check before citing AI-deliberation research, the model never pre-writes what a room must author
• Visual identity: palette tokens with hexes, DM Sans at body weight 300, radius 0 + pill buttons, perfect-fourth type scale, PhosphorIcons
• Working with named people: 2-4 sentence limit when publishing in someone's voice; "the board" terminology

Deliberately complements rather than duplicates docs/_authoring/STYLE.md, which stays the authority for docs pages. Sensitive internal context (partner names in critique positions, internal file paths) was intentionally left out since this repo is public.

🤖 Generated with Claude Code

[github-actions]

Hi @JorimTheuns!

Thank you for contributing to Dembrane ECHO! Before we consider your Pull Request, we ask that you sign our Contributor License Agreement (CLA). This is only required for your first Pull Request.

Please review the CLA, and sign it by adding your GitHub username to the contributors.yml file. Thanks!