Add Example Pre-Race Scenario

[ethancoon]

Description

Add an example pre-race scenario using Rivanna 3S placeholder parameters and a simple test course.

The example should:

• Use offline synthetic weather
• Reference Rivanna 3S parameters or current placeholder parameters
• Use a simple course definition
• Demonstrate a basic constant-speed planning run
• Be easy for new contributors to run locally

Acceptance Criteria

• An example scenario file exists.
• An example course file exists.
• The example uses offline synthetic weather.
• The example references Rivanna 3S or placeholder car parameters.
• The example can be run locally with a documented command.
• The README or relevant docs mention how to run the example.

Notes

This is mainly a usability and onboarding task for the scenario workflow.

References

• Add Scenario File Format #59
• Add Course Definition File Format #60
• Add Scenario Loader #61
• Add CLI Option To Run Simulator Without Weather API #46
• Add Deterministic Synthetic Weather For Tests #43