96d605b9de
Drop "half" from _VALID_DTYPE_OVERRIDES / _LOW_PRECISION_DTYPES. get_dtype() has never accepted "half", so VOXCPM_MPS_DTYPE=half would pass override validation and then crash downstream with "Unsupported dtype: half". The remaining aliases (bfloat16/bf16, float16/fp16, float32/fp32) already cover the intended dtype space. Adds a standalone unit check under scripts/ to guard the invariant that every accepted override parses through get_dtype(). Addresses review feedback on #263.