movenet.cpp — Phase 3 placeholder

ggml port of Google MoveNet (MultiPose Lightning) for keypoint detection.

Status: not started. See plugins/plugin-vision/VISION_RUNTIME_MIGRATION.md ("Phase 3 plan" / "MoveNet (pose)") for the conversion strategy.

Until this port lands, src/vision-models.ts::detectPoses continues to depend on @tensorflow/tfjs-node + @tensorflow-models/pose-detection. Those deps are scheduled for removal once MoveNet ggml is built.