The int8 build quantized only the tied logit head, leaving the rest of the
decoder in fp32. Quantizing every decode-side linear takes the file from
154 MB to 130 MB with a transcript identical to the fp32 decoder.
Encode is untouched and its output is bit-identical to the fp16 variant:
the cross-attention key and value projections are excluded, since the
encoder hoists them and they run in the Vulkan partition.
Exported with the conv1d-as-conv2d lowering, the slice-based STFT magnitude,
hoisted cross-attention K/V and a head-major KV layout. Requires the ExecuTorch
1.4.1 Vulkan runtime from the v0.10.0-libs-1.4.1 artifacts (gelu clamp, reduce
barrier and Adreno local-work-group fixes).
