What's the problem this feature will solve?
Currently, when working with Scenario instances, there is no simple way to:

• retrieve only the scenario parameters while excluding internal metadata (model, _scenario_id)
• create a modified copy of an existing scenario with updated parameters

This makes experiment sweeps, logging, and reproducibility cumbersome and error-prone.

Describe the solution you'd like
Add two small utility methods to the Scenario class:

1. get_parameters() – returns scenario parameters excluding metadata.
2. copy(**updates) – creates a new scenario instance with optional parameter updates:
   • assigns a new _scenario_id
   • does not copy the model reference
   • shares the same RNG object by reference

These additions would simplify scenario management and improve usability for experiments.

Additional context

• A PR implementing this already exists: Add parameter access and copy support to Scenario #3158
• The copy() method is useful for creating slightly modified scenarios for sweeps or testing different parameters without affecting the original instance.
• The RNG sharing behavior is documented to prevent confusion.