refactor: rename command files for namespace consistency

BREAKING CHANGE: All generic command names now prefixed with plugin namespace.
See CHANGELOG.md v7.0.0 for complete rename map.

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

plugins/viz-platform/commands/viz-theme.md

@@ -0,0 +1,45 @@
+---
+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
+
+```
++------------------------------------------------------------------+
+|  VIZ-PLATFORM - Apply Theme                                      |
++------------------------------------------------------------------+
+```
+
+Apply an existing theme to activate its design tokens.
+
+## Usage
+
+```
+/theme {name}
+```
+
+## Arguments
+
+- `name` (required): Theme name to activate
+
+## Tool Mapping
+
+```python
+theme_activate(theme_name="dark")
+theme_list()  # List available themes
+```
+
+## Theme Effects
+
+When activated, new charts/layouts automatically use theme tokens.
+
+## Related Commands
+
+- `/theme-new {name}` - Create a new theme
+- `/theme-css {name}` - Export theme as CSS