fix: close temp file handle before GCS blob download

[Copilot]

download_gcs_blob() called blob.download_to_filename(tmp.name) while the NamedTemporaryFile handle was still open, causing file-locking failures on Windows and potential write conflicts.

Change

Move tmp.close() to before the download call, releasing the handle before writing:

# Before
tmp = tempfile.NamedTemporaryFile(delete=False, suffix=suffix, prefix="dmaf_gcs_")
blob.download_to_filename(tmp.name)  # handle still open
tmp.close()

# After
tmp = tempfile.NamedTemporaryFile(delete=False, suffix=suffix, prefix="dmaf_gcs_")
tmp.close()  # release handle first
blob.download_to_filename(tmp.name)

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