Helper module containing macro code for use Jido.Signal.

This module provides the define_signal_functions/0 macro that generates all the necessary functions for a custom Signal module, including:

• Accessor functions (type/0, default_source/0, etc.)
• Constructor functions (new/0, new/1, new/2, new!/0, new!/1, new!/2)
• Validation functions (validate_data/1)
• Serialization helpers (to_json/0, __signal_metadata__/0)