[codex] add reward debugging guide

[salim4n]

Closes #56

What changed

• Added a reward debugging guide around named reward terms and replay frames.
• Shows how to compare a failed random run with an improved trained DroneTarget run.
• Documents common reward bugs, symptoms and what to inspect.
• Maps CLI commands and exported artifacts to future Studio panels.

Validation

• Verified the documented DroneTarget demo/compare/rewards/replay commands against a local project.
• bun run ci