fix(core.utils): keep path-backed ObjectCode error message Windows-friendly

`{code!r}` doubles every backslash on Windows, so the error string holds
`'C:\\Users\\...\\file'` while `str(src)` only has single
backslashes. Naive `str(path) in str(exc)` checks (and the
`test_filestream_cache_path_backed_object_code_missing_file_message`
assertion) failed on win-64 as a result. Drop the `!r` so the path
appears verbatim; the message still quotes it via the surrounding
sentence punctuation.

Author: cpcloud

cuda_core/cuda/core/utils/_program_cache/_abc.py

@@ -30,8 +30,11 @@ def _extract_bytes(value: object) -> bytes:
             try:
                 return Path(code).read_bytes()
             except FileNotFoundError:
+                # Avoid ``{code!r}``: on Windows it doubles every backslash in
+                # the path, which breaks naive ``str(path) in str(exc)`` checks
+                # callers (and tests) write against the raw filesystem string.
                 raise FileNotFoundError(
-                    f"cannot store path-backed ObjectCode in cache: {code!r} no longer exists"
+                    f"cannot store path-backed ObjectCode in cache: {code} no longer exists"
                 ) from None
         return bytes(code)
     raise TypeError(f"cache values must be bytes-like or ObjectCode, got {type(value).__name__}")