Visible warning for unrecognized modifier kinds

Demo/App.swiftpm/Sources/AppearancePlaygrounds.swift

@@ -44,7 +44,24 @@ struct AppearancePlayground: View {
                             Text("Centered overlay").foregroundColor(.white).bold()
                         }
                 }
+                Example("Unknown modifier → red outline") {
+                    Text("Carries a modifier the interpreter doesn't recognize")
+                        .padding()
+                        .unrecognizedModifier()
+                }
             }
         }
     }
 }
+
+/// A stand-in for a modifier the interpreter has no fold for — emits a kind
+/// outside the known set, so the renderer flags it with a red outline.
+struct _UnrecognizedModifier: RenderModifier {
+    var _modifierNode: ModifierNode { ModifierNode(kind: "notImplementedInInterpreter") }
+}
+
+extension View {
+    func unrecognizedModifier() -> ModifiedContent<Self, _UnrecognizedModifier> {
+        modifier(_UnrecognizedModifier())
+    }
+}

Demo/swiftui/src/commonMain/kotlin/com/pureswift/swiftui/Render.kt

@@ -980,12 +980,27 @@ internal fun ViewNode.composeModifiers(): Modifier {
                 if (off) modifier.alpha(0.38f) else modifier
             }
 
-            else -> modifier // unknown modifier: ignore, never crash rendering
+            else -> modifier // consumed elsewhere (Text/RenderChild/effects) or unknown
         }
     }
+    // Schema-drift visibility: a kind no consumer recognizes gets a red outline,
+    // the modifier-level analog of the unknown-node diagnostic.
+    if (modifiers.any { it.kind !in KNOWN_MODIFIER_KINDS }) {
+        modifier = modifier.border(1.dp, Color.Red)
+    }
     return modifier
 }
 
+// Every modifier kind some consumer handles — composeModifiers folds most;
+// the rest are read by RenderText, RenderChild (environment), RenderEffects, or
+// container branches (tag/tabItem). A kind outside this set is schema drift.
+private val KNOWN_MODIFIER_KINDS = setOf(
+    "padding", "frame", "background", "cornerRadius", "offset", "rotation",
+    "scale", "opacity", "border", "shadow", "clipShape", "onTapGesture", "disabled",
+    "font", "fontWeight", "italic", "foregroundColor", "lineLimit", "multilineTextAlignment",
+    "tint", "onAppear", "onDisappear", "task", "onChange", "animation", "tag", "tabItem",
+)
+
 // Folds a frame entry: fixed size, fill (maxWidth/Height .infinity), bounded
 // (widthIn/heightIn), and content alignment within the resulting box.
 @Composable