GeezerVison

Fixes gh-161081.

PyObject_CopyData() used source-buffer indices for both buffers on its non-contiguous copy path. When their shapes differed, this could write to incorrect offsets or read beyond the source index array. Validate that non-contiguous source and destination buffers have the same dimensions and shape before copying.

Add a regression test using _testbuffer arrays with different shapes. The test failed before this change because the copy returned success; it now raises BufferError.

Tests:

• PCbuild\\build.bat -d -p x64 -M -q
• PCbuild\\amd64\\python_d.exe -m test -v -m test_mismatched_shape test_buffer
• PCbuild\\amd64\\python_d.exe -m test -v test_buffer (98 passed, 2 skipped)
• PCbuild\\amd64\\python_d.exe Tools\\patchcheck\\patchcheck.py

AI assistance was used to investigate the issue and prepare this change. I reviewed the code and test behavior, including the failing pre-fix regression, before opening this PR.