docs: note safetensors-only mirror policy

README.md

@@ -16,7 +16,9 @@ base_model: facebook/mask2former-swin-tiny-coco-instance
 
 Apache-2.0 mirror hosted under `CondadosAI/` for use with the [acaua](https://github.com/CondadosAI/acaua) computer vision library.
 
-This is a **1:1 byte-identical copy** of the upstream Meta AI Research weights at the pinned commit shown below. We do not modify weights or configuration. The purpose of the mirror is license hygiene: acaua's core promise is that every shipped weight has an auditable, declared Apache-2.0 upstream. Mirroring lets us pin a specific revision so the audit claim stays verifiable even if upstream rewrites history.
+This is a **safetensors-only mirror** of the upstream Meta AI Research weights at the pinned commit shown below. The `model.safetensors` file is byte-identical to upstream; we do not modify weights or configuration. The legacy `pytorch_model.bin` (pickle format) that upstream ships alongside safetensors has been **deliberately removed** from this mirror for security hygiene — pickle loads can execute arbitrary code, and `transformers` auto-prefers safetensors when both are present, so removing it has zero functional impact on downstream users.
+
+The purpose of the mirror is license hygiene: acaua's core promise is that every shipped weight has an auditable, declared Apache-2.0 upstream. Mirroring lets us pin a specific revision so the audit claim stays verifiable even if upstream rewrites history.
 
 ## Provenance