Clarify third-person orbit direction semantics

[Arison591]

Summary

• describe third-person left/right prompts using the subject side instead of ambiguous clockwise wording
• document the yaw-sign and camera-coordinate convention in both navigation-to-pose adapters
• add regression coverage for action mappings, generated orbit positions, and prompt wording

The numerical pose generation is intentionally unchanged. This makes the language match the existing subject-relative control semantics without depending on a viewpoint-specific clockwise interpretation.

Addresses #9.

Testing

• python -m unittest discover -s tests -v
• python -m compileall -q src/models examples/hy_worldplay tests
• git diff --check