Fix NvDec decoder stale state when cropping (#1165)

This commit address an issue where executing
`test_nvdec_decode_crop_resize` before
`test_nvdec_decode_h264_420p_crop` causes the latter to return wrong
results
due to bad state left behind. 

~The fix involves modifying the `NvDecDecoderCore::reset()` method to
properly clean up state,
including resetting crop, target width and height, and source
information to default values.
This ensures that the thread-local cached decoder does not carry over
stale parameters from previous test runs.~

Modifying the `NvDecDecoderCore` is more elaborated, so, for now, we
disable cache if crop is provided.

~This commit also adds the stand alone test that would repro the issue
without the patch.~
Moved to 7619393 as the test manifests
a different issue.

- w/o fix
https://github.com/facebookresearch/spdl/actions/runs/19650268816
- w/ fix
https://github.com/facebookresearch/spdl/actions/runs/19641739313

Closes #1159

Author: mthrok

src/spdl/io/_core.py

@@ -1039,6 +1039,11 @@ def nvdec_decoder(
         The old pattern of calling ``decoder.init()`` after ``nvdec_decoder()``
         will be removed in a future version.
     """
+    # Force recreation if crop is provided, regardless of use_cache
+    crop_params = (crop_left, crop_top, crop_right, crop_bottom)
+    if any(param != 0 for param in crop_params):
+        use_cache = False
+
     if use_cache:
         decoder = _get_decoder()
         decoder.reset()