feat(interface-design): add comprehensive interface design skill documentation and references

- Introduced SKILL.md outlining the principles and processes for effective interface design.
- Added critique.md for evaluating design outputs and ensuring craft over correctness.
- Created example.md to illustrate the application of subtle layering principles in design decisions.
- Developed principles.md detailing core craft principles for consistent design quality.
- Implemented validation.md for memory management and pattern reuse in the design system.
- Established system.md for the Playzer design system, defining direction, domain concepts, and design decisions.
- Added StatusBadge component for displaying booking statuses with appropriate styles and labels.
- Updated skills-lock.json to include the new interface-design skill.

.agents/skills/interface-design/references/validation.md

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+# Memory Management
+
+When and how to update `.interface-design/system.md`.
+
+## When to Add Patterns
+
+Add to system.md when:
+- Component used 2+ times
+- Pattern is reusable across the project
+- Has specific measurements worth remembering
+
+## Pattern Format
+
+```markdown
+### Button Primary
+- Height: 36px
+- Padding: 12px 16px
+- Radius: 6px
+- Font: 14px, 500 weight
+```
+
+## Don't Document
+
+- One-off components
+- Temporary experiments
+- Variations better handled with props
+
+## Pattern Reuse
+
+Before creating a component, check system.md:
+- Pattern exists? Use it.
+- Need variation? Extend, don't create new.
+
+Memory compounds: each pattern saved makes future work faster and more consistent.
+
+---
+
+# Validation Checks
+
+If system.md defines specific values, check consistency:
+
+**Spacing** — All values multiples of the defined base?
+
+**Depth** — Using the declared strategy throughout? (borders-only means no shadows)
+
+**Colors** — Using defined palette, not random hex codes?
+
+**Patterns** — Reusing documented patterns instead of creating new?