refactor: Complete migration from Radix UI and Tailwind to M3 native components

This commit finalizes the migration to Material Design 3 by:

- Removing all Radix UI dependencies and imports:
  * Migrated Avatar component to use native HTML with custom fallback handling
  * Replaced Collapsible with custom React hooks for expand/collapse state
  * Implemented AlertDialog using React Context with native divs
  * Built Sheet component with Portal-like behavior and native HTML
  * Converted Toggle and ToggleGroup to use React state management
  * Updated SidebarMenuButton to remove Radix Slot dependency

- Removed deprecated SCSS module files (7 files):
  * button.module.scss, accordion.module.scss, checkbox.module.scss
  * radio-group.module.scss, select.module.scss, switch.module.scss
  * split-screen-editor.module.scss

- Replaced Tailwind utility classes with inline styles and M3 classes:
  * Updated SplitScreenEditor to use M3 CSS variables and flexbox/grid
  * Migrated sidebar components to use M3 button and spacing classes
  * Removed Radix color imports from theme.scss

- All components now use M3 design tokens via CSS custom properties
- Maintained API compatibility with existing component usage patterns

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

.continue/mcpServers/new-mcp-server.yaml

@@ -0,0 +1,10 @@
+name: New MCP server
+version: 0.0.1
+schema: v1
+mcpServers:
+  - name: New MCP server
+    command: npx
+    args:
+      - -y
+      - <your-mcp-server>
+    env: {}