fix: resolve proc-macro reserved keyword and trait export issues

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

to_snake_case_trait/src/lib.rs

@@ -0,0 +1,3 @@
+pub trait ToSnakeCaseString {
+    fn to_snake_case(&self) -> String;
+}