fix: streaming validator — surface limit errors, reject unknown args

- Go: append error to v.errors before setting StateError on buffer/field limit hit
- Go/JS/Rust: record error on unknown argument instead of silent return
- Matches Python reference behavior for cross-runtime parity

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: phenomenon0

go/glyph/stream_validator.go

@@ -308,10 +308,18 @@ func (v *StreamingValidator) PushToken(token string) *StreamValidationResult {
 func (v *StreamingValidator) processChar(char rune) {
 	// Check hard limits before processing
 	if v.buffer.Len() >= v.maxBufferSize {
+		v.errors = append(v.errors, StreamValidationError{
+			Code:    ErrCodeLimitExceeded,
+			Message: "Buffer size limit exceeded",
+		})
 		v.state = StateError
 		return
 	}
 	if len(v.parsedFields) >= v.maxFieldCount {
+		v.errors = append(v.errors, StreamValidationError{
+			Code:    ErrCodeLimitExceeded,
+			Message: "Field count limit exceeded",
+		})
 		v.state = StateError
 		return
 	}
@@ -470,6 +478,11 @@ func (v *StreamingValidator) validateField(key string, value interface{}) {
 
 	argSchema, exists := schema.Args[key]
 	if !exists {
+		v.errors = append(v.errors, StreamValidationError{
+			Code:    ErrCodeUnknownTool,
+			Message: fmt.Sprintf("Unknown argument: %s", key),
+			Field:   key,
+		})
 		return
 	}
 

js/src/stream_validator.ts

@@ -524,6 +524,7 @@ export class StreamingValidator {
 
     const argSchema = hasOwn(schema.args, key) ? schema.args[key] : undefined;
     if (!argSchema) {
+      this.addError(ErrorCode.UnknownTool, `Unknown argument: ${key}`, key);
       return;
     }
 

rust/glyph-codec/src/stream_validator.rs

@@ -608,7 +608,13 @@ impl StreamingValidator {
 
         let arg_schema = match schema.args.get(key).cloned() {
             Some(s) => s,
-            None => return,
+            None => {
+                self.add_error(
+                    ValidationError::new(ErrorCode::UnknownTool, &format!("Unknown argument: {}", key))
+                        .with_field(key),
+                );
+                return;
+            }
         };
 
         if !Self::type_matches(&arg_schema, value) {