refactor(viz-platform): extract skills and slim commands

Extract shared knowledge from 10 commands into 7 reusable skills:
- mcp-tools-reference.md: All viz-platform MCP tool signatures
- theming-system.md: Theme tokens, CSS variables, color palettes
- accessibility-rules.md: WCAG contrast, color-blind safe palettes
- dmc-components.md: DMC categories, validation, common props
- responsive-design.md: Breakpoints, mobile-first, grid config
- chart-types.md: Plotly chart types, export formats, resolution
- layout-templates.md: Dashboard templates, filter types

All commands now reference skills via "Skills to Load" section.
Commands reduced from 1396 lines total to 427 lines (69% reduction).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/viz-platform/skills/accessibility-rules.md

@@ -0,0 +1,64 @@
+# Accessibility Rules
+
+## WCAG Contrast Standards
+
+| Level | Ratio | Use Case |
+|-------|-------|----------|
+| AA (normal text) | 4.5:1 | Body text, labels |
+| AA (large text) | 3:1 | Headings, 14pt+ bold |
+| AAA (enhanced) | 7:1 | Highest accessibility |
+
+## Color Blindness Types
+
+| Type | Affected Colors | Population |
+|------|-----------------|------------|
+| **Deuteranopia** | Red-Green (green-blind) | ~6% males, 0.4% females |
+| **Protanopia** | Red-Green (red-blind) | ~2.5% males, 0.05% females |
+| **Tritanopia** | Blue-Yellow | ~0.01% total |
+
+## Color-Blind Safe Palettes
+
+### IBM Design Colors
+```
+#648FFF #785EF0 #DC267F #FE6100 #FFB000
+```
+
+### Tableau Colorblind 10
+```
+#006BA4 #FF800E #ABABAB #595959 #5F9ED1
+#C85200 #898989 #A2C8EC #FFBC79 #CFCFCF
+```
+
+### Okabe-Ito
+```
+#E69F00 #56B4E9 #009E73 #F0E442 #0072B2
+#D55E00 #CC79A7 #000000
+```
+
+### Safe Palette Categories
+
+```json
+{
+  "categorical": ["#4477AA", "#EE6677", "#228833", "#CCBB44", "#66CCEE", "#AA3377", "#BBBBBB"],
+  "sequential": ["#FEE0D2", "#FC9272", "#DE2D26"],
+  "diverging": ["#4575B4", "#FFFFBF", "#D73027"]
+}
+```
+
+## Best Practices
+
+1. **Don't rely on color alone** - Use shapes, patterns, or labels
+2. **Test with simulation** - View through color blindness simulators
+3. **Use sufficient contrast** - Minimum 4.5:1 for text, 3:1 for large elements
+4. **Limit color count** - Fewer colors = easier to distinguish
+5. **Use semantic colors** - Blue for information, red for errors (with icons)
+
+## Accessibility Scoring
+
+| Grade | Description |
+|-------|-------------|
+| A | Excellent - All WCAG AAA standards met |
+| B | Good - WCAG AA standards met with minor warnings |
+| C | Acceptable - WCAG AA met but improvements recommended |
+| D | Poor - Some WCAG AA failures |
+| F | Failing - Major accessibility issues |