fix: fail closed on hf streaming extensionless listings

[mldangelo-oai]

Summary

• remove the HuggingFace streaming all-file fallback when no recognized scannable files are listed
• fail closed instead of downloading every extensionless/non-model file from large repos
• add a large extensionless listing regression and known-extension guard

Validation

• PYTHONPATH=/private/tmp/modelaudit-c187 PROMPTFOO_DISABLE_TELEMETRY=1 /Users/mdangelo/code/modelaudit/.venv/bin/pytest tests/utils/sources/test_huggingface.py -q: 56 passed
• ruff format/check for touched files
• mypy modelaudit/utils/sources/huggingface.py tests/utils/sources/test_huggingface.py
• git diff --check

[mldangelo-oai]

@codex review

[github-actions]

Workflow run and artifacts

Performance Benchmarks

Compared 12 shared benchmarks with a regression threshold of 15%.
Status: 0 regressions, 0 improved, 12 stable, 0 new, 0 missing.
Aggregate shared-benchmark median: 759.27ms -> 756.61ms (-0.4%).

Workload	Benchmark	Target	Size	Files	Baseline	Current	Change	Status
nested-payload-review	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_nested_payload_review[nested_hex]	nested_hex	130 B	1	434.1us	410.3us	-5.5%	stable
warm-cache-rescan	tests/benchmarks/test_scan_benchmarks.py::test_scan_warm_cached_repository_rescan	release-candidate	547.3 KiB	32	66.88ms	63.94ms	-4.4%	stable
nested-payload-review	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_nested_payload_review[nested_raw]	nested_raw	78 B	1	413.8us	400.7us	-3.2%	stable
padded-multi-stream-upload	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_padded_multi_stream_upload	multi_stream_padded	4.1 KiB	1	1.54ms	1.51ms	-2.2%	stable
nested-payload-review	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_nested_payload_review[nested_base64]	nested_base64	98 B	1	415.0us	423.5us	+2.1%	stable
direct-malicious-upload	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_direct_malicious_upload	malicious_reduce	52 B	1	1.46ms	1.44ms	-1.2%	stable
suspicious-pickle-intake	tests/benchmarks/test_scan_benchmarks.py::test_scan_suspicious_pickle_intake	suspicious-intake	183.8 KiB	4	99.36ms	98.46ms	-0.9%	stable
mixed-model-repository	tests/benchmarks/test_scan_benchmarks.py::test_scan_release_candidate_repository	release-candidate	547.3 KiB	32	290.18ms	292.07ms	+0.7%	stable
single-checkpoint-preflight	tests/benchmarks/test_scan_benchmarks.py::test_scan_single_checkpoint_before_load	single_checkpoint.pkl	183.0 KiB	1	40.67ms	40.46ms	-0.5%	stable
duplicate-heavy-registry	tests/benchmarks/test_scan_benchmarks.py::test_scan_duplicate_registry_snapshot	registry-snapshot	915.2 KiB	13	215.79ms	215.41ms	-0.2%	stable
chunked-upload-stream	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_chunked_upload_stream	chunked_stream	278.2 KiB	1	22.60ms	22.57ms	-0.1%	stable
clean-training-checkpoint	tests/benchmarks/test_picklescan_benchmarks.py::test_picklescan_clean_training_checkpoint	safe_large	278.2 KiB	1	19.53ms	19.52ms	-0.1%	stable

[chatgpt-codex-connector]

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Reviewed commit: dae3af31c5

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[ianw-oai]

Reviewed; this looks acceptable.