docs: warn on gfx1151 Windows Python 3.14

[Rohithmatham12]

Summary

• Add a visible Windows Python-version note to the shared pytorch dependency for halo/halo_box (gfx1151).
• Add a hidden preflight test before the ROCm PyTorch install that exits with an actionable message on Windows Python 3.14.
• Keep the existing PyTorch package pins and install commands unchanged.

Why
Addresses #315. The current gfx1151 ROCm PyTorch index has Windows wheels for Python cp310-cp313, while Linux includes cp314. On Windows Python 3.14, the playbook currently reaches the pip resolver and fails with a generic no-matching-distribution error. This makes the limitation clear before the install step and tells users to recreate the venv with Python 3.13 or earlier.

Validation

• python3 .github/scripts/validate_playbooks.py
• Extracted pytorch-rocm-llms tests for windows/linux + halo and verified check-gfx1151-python-version is hidden and runs before install-pytorch.
• git diff --check
• Checked https://repo.amd.com/rocm/whl/gfx1151/torch/: torch 2.11.0+rocm7.13.0 Windows tags are cp310-cp313; Linux tags are cp310-cp314.