v4.3.0rc0

Added

• #3710 MCP: Framework utilities, types for interacting with layout
• #3711 MCP: CallbackAdapter for representing callback-related data in MCP-friendly format
• #3712 MCP: Resources for exposing app layout, components, and pages
• #3731 MCP: Expose callbacks as Tools
• #3747 MCP: Support pattern-matching callbacks in Tools
• #3748 MCP: Format callback results for LLM consumption (rendered graphs, markdown tables)
• #3749 MCP: get_dash_component Tool and callback execution
• #3750 MCP: Server routes, mcp_enabled function decorator, and Streamable HTTP transport
• #3766 MCP: Support background callbacks in Tools