Follow-up to the override work in this PR: the get_torch_index_url / install.sh
reroute already respect a pinned UNSLOTH_TORCH_INDEX_URL / _FAMILY, but the
Python repair helpers in install_python_stack.py still re-probed the GPU and
could overwrite the pinned family. Make the pin authoritative there too:
- _ensure_cuda_torch: an explicit cu* pin commits to CUDA wheels, so repair a
ROCm-poisoned venv even when no NVIDIA GPU is visible here (headless /
container / CI cross-install), instead of bailing on the GPU-presence gate.
- _ensure_rocm_torch: skip the AMD per-gfx (Strix) reroute when a ROCm index is
pinned, and in the generic reinstall path install from the pinned URL verbatim
rather than re-detecting the host ROCm version. gfx*/rocm7.2 indexes serve
torch 2.11+, so select the 2.11 package specs for a gfx leaf.
- install.sh: raise the torch constraint to 2.11 for */gfx* indexes too, matching
rocm7.2, so a pinned full-URL/family override that returns early keeps a valid
constraint.
Add _explicit_torch_index_url / _explicit_rocm_torch_index_url helpers and tests
covering the no-GPU CUDA pin repair and the explicit gfx index honored verbatim.
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