Create a new ToolType to remove string literals

[jirispilka]

/**
 * Tool type constants
 * Use these constants instead of string literals for better type safety and maintainability.
 */
export const ToolType = {
    INTERNAL: 'internal',
    ACTOR: 'actor',
    ACTOR_MCP: 'actor-mcp',
} as const;

/**
 * Type for tool type values.
 */
export type ToolType = typeof ToolType[keyof typeof ToolType];