[codex] Hash-truncate long cache path segments

[hansent]

Summary

• Add deterministic hash truncation for path segments longer than the Linux NAME_MAX limit.
• Route Roboflow metadata and model artifact cache paths through the safe join helper.
• Update direct cache path users and air-gapped cache detection to use the same bounded layout.
• Add regression coverage for long instant-model slugs.

Why

Serverless deployments were seeing OSError: [Errno 36] File name too long when instant model IDs produced very long cache directory names. The issue is per path segment, so the fix canonicalizes each segment before writing or reading cache files.

Validation

• .venv/bin/python -m black --check inference/core/utils/file_system.py inference/core/cache/model_artifacts.py inference/core/registries/roboflow.py inference/core/models/roboflow.py inference/models/transformers/transformers.py inference/models/grounding_dino/grounding_dino.py inference/models/easy_ocr/easy_ocr.py inference/core/cache/air_gapped.py tests/inference/unit_tests/core/utils/test_file_system.py tests/inference/unit_tests/core/cache/test_model_artifacts.py tests/inference/unit_tests/core/registries/test_roboflow.py
• .venv/bin/python -m isort --check-only inference/core/utils/file_system.py inference/core/cache/model_artifacts.py inference/core/registries/roboflow.py inference/core/models/roboflow.py inference/models/transformers/transformers.py inference/models/grounding_dino/grounding_dino.py inference/models/easy_ocr/easy_ocr.py inference/core/cache/air_gapped.py tests/inference/unit_tests/core/utils/test_file_system.py tests/inference/unit_tests/core/cache/test_model_artifacts.py tests/inference/unit_tests/core/registries/test_roboflow.py
• .venv/bin/pytest tests/inference/unit_tests/core/utils/test_file_system.py tests/inference/unit_tests/core/cache/test_model_artifacts.py tests/inference/unit_tests/core/registries/test_roboflow.py tests/unit/core/cache/test_air_gapped.py