fix(core): make subprocess and temporary file tests portable on Windows

[Jacopos311]

Both changes are complete and verified. Here's a summary of what was done in this PR (closes #39647):

Changes

1. libs/core/tests/unit_tests/test_imports.py — test_importable_all_via_subprocess

• Added import sys.
• Replaced the bare "python" string in the subprocess.run([...]) call with sys.executable.

Why: On Windows, a bare python invocation from a subprocess can resolve to the base Windows PATH interpreter rather than the interpreter running the test (the active uv environment). Since the test imports a module that may only be installed in the uv environment, this previously caused the subprocess import to fail on Windows. Using sys.executable guarantees the subprocess uses the same active interpreter.

2. libs/core/tests/unit_tests/prompts/test_prompt.py — test_from_file_encoding

• Removed the now-unused from tempfile import NamedTemporaryFile import.
• Added from pathlib import Path.
• Refactored the test to use pytest's tmp_path fixture: the file is written with file_path.write_text(template, encoding="cp1252") and subsequently read via PromptTemplate.from_file(file_path, ...), which accepts str | Path.

Why: The original test kept a NamedTemporaryFile open (the file handle stays active inside the with block) while attempting to reopen that same path. On Windows this triggers a PermissionError due to file locking. Using tmp_path writes and closes the file before any subsequent reads, avoiding the lock entirely while keeping the temporary-file cleanup behavior.

Verification

• Ran both affected tests with uv run pytest: 2 passed.
• Ran ruff check and ruff format --check on both files: all checks passed.

No public API signatures were changed — these are test-only modifications.

[github-actions]

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[codspeed-hq]

Merging this PR will not alter performance

✅ 15 untouched benchmarks
⏩ 2 skipped benchmarks¹

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_{Comparing Jacopos311:fix-windows-tests (9db6d14) with master (b5e8e2e)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩