Improve error handling in generator

- Use two-value form for type assertion to avoid panic
- Use %q for consistent string formatting in error messages

Author: bendrucker

rules/models/generator/main.go

@@ -109,7 +109,7 @@ func main() {
 
 				model := findShape(shapes, shapeName)
 				if model == nil {
-					fmt.Printf("Shape `%s` not found, skipping\n", shapeName)
+					fmt.Printf("Shape %q not found, skipping\n", shapeName)
 					continue
 				}
 

rules/models/generator/rule.go

@@ -93,7 +93,11 @@ func fetchStrings(model map[string]interface{}, key string) []string {
 		case []interface{}:
 			ret := make([]string, len(v))
 			for i, item := range v {
-				ret[i] = item.(string)
+				str, ok := item.(string)
+				if !ok {
+					return []string{}
+				}
+				ret[i] = str
 			}
 			return ret
 		case []string: