Summary

This PR adds static dependency injection to the @computed_property decorator via a new dependencies keyword argument. This allows derived states to manually subscribe to specific signals, explicitly supporting events generated by the @emit decorator which are otherwise invisible to the reactive system.

Motive

See #3227

Implementation

• Decorator Expansion: Updated @computed_property to accept a dependencies kwarg, which takes a list of tuples containing the target dependencies name and the specific signal types (or pass nothing for ALL sentinel).
• State Initialization: Modified ComputedState.__init__ to parse the dependencies list upon creation.
• Lifecycle Wiring: For each dependency provided, the ComputedState actively registers itself with the target using owner.observe(obs_name, signal_type, self._set_dirty). This bypasses the need for __get__ auto-discovery and directly injects the cache invalidation trigger into the emitter's internal subscribers dictionary.

Usage Examples

from mesa.experimental.mesa_signals import HasEmitters, computed_property, emit, ModelSignals

class MyModel(mesa.Model):
    def __init__(self):
        super().__init__()
        self.agent_count = 0

    @emit("model", ModelSignals.AGENT_ADDED)
    def add_agent(self):
        self.agent_count += 1

    # Statically bridging the built-in signal to the computed property
    @computed_property(dependencies=[("model", ModelSignals.AGENT_ADDED)])
    def population_status(self):
        return "Populated" if self.agent_count > 0 else "Empty"