P0-04: Define skeleton connectivity and output schema

[McMabee]

Summary

Define how keypoints connect into a skeleton and how CreaseTrack v1 outputs predictions in a consistent machine-readable format.

Objective

Create a stable schema contract that any baseline model can emit and any evaluation pipeline can consume.

Scope

• Skeleton connectivity
• Output fields
• Missing-point behavior
• Coordinate and confidence representation

Deliverable

• docs/skeleton_schema_v1.md

Acceptance Criteria

• Skeleton connections are defined
• Output fields are defined, including:
  • frame id
  • clip id
  • timestamp
  • keypoint name
  • x
  • y
  • visibility flag
  • confidence
• Missing-point handling is defined
• Behavior for null vs hidden vs extrapolated is documented
• Schema is consistent enough for future model outputs and evaluation scripts

Notes

Complete P0-03 before finalizing this ticket.