feature5 implementation is full now

canvas/src/validation/mod.rs

@@ -16,6 +16,16 @@ pub use patterns::{PatternFilters, PositionFilter, PositionRange, CharacterFilte
 pub use mask::DisplayMask;  // Simple mask instead of ReservedCharacters
 pub use formatting::{CustomFormatter, FormattingResult, PositionMapper, DefaultPositionMapper};
 
+/// External validation UI state (Feature 5)
+#[derive(Debug, Clone, PartialEq, Eq)]
+pub enum ExternalValidationState {
+    NotValidated,
+    Validating,
+    Valid(Option<String>),
+    Invalid { message: String, suggestion: Option<String> },
+    Warning { message: String },
+}
+
 /// Validation error types
 #[derive(Debug, Clone, thiserror::Error)]
 pub enum ValidationError {