Update experimental weights with private Exam-QA pilot

Document PyPI ERABI 0.1.2 availability

Link current GitHub runtime until PyPI 0.1.2

Clarify ERABI version required for ONNX selection

Document Practical V1 ONNX runtime variants

Add Practical V1 GPU ONNX FP16 variant

Add Practical V1 CPU ONNX FP32 variant

Use PyPI install command

Show default one-command ERABI usage

Document experimental model provenance and limitations

Add Practical V1 experimental checkpoint

initial commit