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/commands/theme.md

@@ -4,18 +4,18 @@ description: Apply an existing theme to the current context
 
 # Apply Theme
 
+## Skills to Load
+- skills/mcp-tools-reference.md
+- skills/theming-system.md
+
 ## Visual Output
 
-When executing this command, display the plugin header:
-
 ```
-┌──────────────────────────────────────────────────────────────────┐
-│  🎨 VIZ-PLATFORM · Apply Theme                                    │
-└──────────────────────────────────────────────────────────────────┘
++------------------------------------------------------------------+
+|  VIZ-PLATFORM - Apply Theme                                      |
++------------------------------------------------------------------+
 ```
 
-Then proceed with the theme activation.
-
 Apply an existing theme to activate its design tokens.
 
 ## Usage
@@ -28,52 +28,16 @@ Apply an existing theme to activate its design tokens.
 
 - `name` (required): Theme name to activate
 
-## Examples
-
-```
-/theme dark
-/theme corporate-blue
-/theme my-custom-theme
-```
-
 ## Tool Mapping
 
-This command uses the `theme_activate` MCP tool:
-
 ```python
 theme_activate(theme_name="dark")
+theme_list()  # List available themes
 ```
 
-## Workflow
-
-1. **User invokes**: `/theme dark`
-2. **Tool activates**: Theme becomes active for subsequent operations
-3. **Charts/layouts**: Automatically use active theme tokens
-
-## Built-in Themes
-
-| Theme | Description |
-|-------|-------------|
-| `light` | Mantine default light mode |
-| `dark` | Mantine default dark mode |
-
-## Listing Available Themes
-
-To see all available themes:
-
-```python
-theme_list()
-```
-
-Returns both built-in and custom themes.
-
 ## Theme Effects
 
-When a theme is activated:
-- New charts inherit theme colors
-- New layouts use theme spacing
-- Components use theme typography
-- Callbacks can read active theme tokens
+When activated, new charts/layouts automatically use theme tokens.
 
 ## Related Commands