Prepare Traffic Lights Arena participant starter

[KerrikStone]

Summary

• Align the participant simulator with the competition engine
• Add the team login and submission workflow
• Improve the local viewer and documentation
• Expand simulator verification

Verification

• Starter simulator checks passed
• Participant login and submission-client flow passed
• Shared engine and scoring files match the platform

[DVerdeV]

Implemented the thermos follow-up fixes in two conventional commits:

• d0e99b8 — fix(simulator): encode yellow signal direction
  • emits replay contract v2 with explicit NS_YELLOW / EW_YELLOW phases
  • adds transition-contract coverage
• 30dfe3b — fix(viewer): consume replay phases and surface errors
  • removes per-frame replay-history scans from rendering
  • rejects unsupported replay versions
  • displays polling, HTTP, and empty-replay failures instead of swallowing them

The downloadable starter ZIP and matching private simulator artifacts were regenerated in DVerdeV/CursorBuildNight#1.

Verification completed:

• 4 pytest tests
• viewer JavaScript syntax check
• cross-repository simulator source parity
• starter ZIP/schema artifact validation
• git diff --check