card: Swift usage via coreai-kit SafetyClassifier

README.md

@@ -101,6 +101,18 @@ SUFFIX = "[/INST]"
 
 **Not included:** the checkpoint's Pixtral vision tower (`image_size` 1540). Text only.
 
+## Using it from Swift
+
+```swift
+let guard = try await SafetyClassifier(model: .shieldstral3B)   // .shieldstral3BShort for S=256
+let verdict = try await guard.check(message, policy: .selfHarm)
+```
+
+[coreai-kit](https://github.com/john-rocky/coreai-kit)'s `SafetyClassifier` owns the scaffolding,
+the padding and the threshold. `reference.json` in each bundle ships the nine gated cases with
+their fp32 probabilities, so any host — Swift, Python, yours — can check its own prompt
+construction rather than trusting it.
+
 ## Converting it yourself
 
 The conversion venv here is transformers 4.57.6, which cannot load this checkpoint at all — the