Add UK AI principles framework scaffold (5 packages)

[kmadan]

Goal

Bootstrap `international/uk_ai_principles/v1/` covering the five principles from the UK pro-innovation regulatory framework:

1. Safety, security, robustness
2. Appropriate transparency and explainability
3. Fairness
4. Accountability and governance
5. Contestability and redress

Why this matters

UK governance teams have been asking for an executable mapping. Full coverage on day one isn't expected — five `default allow := false` scaffolds with named obligations and metadata is enough to open the contributor pipeline.

How to scaffold

Use the add-framework Claude Code skill to generate the directory tree, framework README, and first stub policy. Or follow docs/tutorials/add-your-first-policy.md.

Acceptance criteria

• `international/uk_ai_principles/v1/` exists with five package subdirectories (one per principle)
• Each package has a Rego file with proper `metadata` block referencing the UK government white-paper text
• Each package has a sibling `*_test.rego` covering at least the default-deny case
• `docs/coverage/uk-ai-principles.md` exists, scoped like the existing matrices
• docs/coverage/README.md links to the new matrix
• `README.md` roadmap section updated to mark UK AI as in-progress
• `opa check`, `opa test`, `regal lint` all pass

Get help

Comment here — happy to pair if you're new to Rego.