feat(viz-platform): complete Sprint 1 - plugin structure and tests

Sprint 1 - viz-platform Plugin completed (13/13 issues):
- Commands: 7 files (initial-setup, chart, dashboard, theme, theme-new, theme-css, component)
- Agents: 3 files (theme-setup, layout-builder, component-check)
- Documentation: README.md, claude-md-integration.md
- Tests: 94 tests passing (68-99% coverage)
- CHANGELOG updated with completion status

Closes: #178, #179, #180, #181, #182

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

plugins/viz-platform/commands/chart.md

@@ -0,0 +1,86 @@
+---
+description: Create a Plotly chart with theme integration
+---
+
+# Create Chart
+
+Create a Plotly chart with automatic theme token application.
+
+## Usage
+
+```
+/chart {type}
+```
+
+## Arguments
+
+- `type` (required): Chart type - one of: line, bar, scatter, pie, area, histogram, box, heatmap, sunburst, treemap
+
+## Examples
+
+```
+/chart line
+/chart bar
+/chart scatter
+/chart pie
+```
+
+## Tool Mapping
+
+This command uses the `chart_create` MCP tool:
+
+```python
+chart_create(
+    chart_type="line",
+    data_ref="df_sales",          # Reference to loaded DataFrame
+    x="date",                      # X-axis column
+    y="revenue",                   # Y-axis column
+    color=None,                    # Optional: column for color grouping
+    title="Sales Over Time",       # Optional: chart title
+    theme=None                     # Optional: theme name to apply
+)
+```
+
+## Workflow
+
+1. **User invokes**: `/chart line`
+2. **Agent asks**: Which DataFrame to use? (list available with `list_data` from data-platform)
+3. **Agent asks**: Which columns for X and Y axes?
+4. **Agent asks**: Any grouping/color column?
+5. **Agent creates**: Chart with `chart_create` tool
+6. **Agent returns**: Plotly figure JSON ready for rendering
+
+## Chart Types
+
+| Type | Best For |
+|------|----------|
+| `line` | Time series, trends |
+| `bar` | Comparisons, categories |
+| `scatter` | Correlations, distributions |
+| `pie` | Part-to-whole relationships |
+| `area` | Cumulative trends |
+| `histogram` | Frequency distributions |
+| `box` | Statistical distributions |
+| `heatmap` | Matrix correlations |
+| `sunburst` | Hierarchical data |
+| `treemap` | Hierarchical proportions |
+
+## Theme Integration
+
+Charts automatically inherit colors from the active theme:
+- Primary color for main data
+- Color palette for multi-series
+- Font family and sizes
+- Background colors
+
+Override with explicit theme:
+```python
+chart_create(chart_type="bar", ..., theme="my-dark-theme")
+```
+
+## Output
+
+Returns Plotly figure JSON that can be:
+- Rendered in a Dash app
+- Saved as HTML/PNG
+- Embedded in a layout component