feat: convert demo files from .md to .tsx for editor support

[wangdicoder]

Summary

Migrate demo files from markdown format (.md) to TypeScript/React format (.tsx) to enable proper IDE support.

Motivation

Previously, demo files were written in markdown format, which limited editor functionality:

• No proper syntax highlighting in many editors
• No type checking or IntelliSense
• Limited refactoring support

By converting to .tsx format, demos now benefit from:

• Full TypeScript type checking
• Proper syntax highlighting in VS Code, WebStorm, and other editors
• IntelliSense and autocompletion
• Better code navigation and refactoring tools

Changes

Demo file migration

• Converted all component demo files from .md to .tsx
• Demo files renamed from kebab-case to PascalCase (e.g., basic.md → Basic.tsx)
• Demo content rewritten as React components with proper imports

Documentation infrastructure

• Updated demo-block component to handle TSX demos
• Added sandbox utilities for safe demo rendering
• Updated locale files with new labels