[ishaanzee]

• ☑️ I understand it is strictly prohibited to use AI to write PR description
• AI usage disclosure: ai helped with the test, docs text and repro script

@zcbenz in #4595:

Sounds good to me to have a MLX_CONV_WINOGRAD switch.

MLX_CONV_WINOGRAD=0 turns off winograd for conv2d. It's read per call, like the other MLX_CONV_WINOGRAD_* vars.

Winograd selection depends on N x H x W, so results change with batch size. Error goes from ~2e-5 to 2.5e-4 from batch 3 up. (can see here #4595 (comment))

• The one condition is in conv.cpp
• docs in environment_variables.rst and precision.rst
• test in python/tests/test_conv.py

the new test fails w/o the change and passes with it, and the full suite passes on my m3 pro (939 passed)