fix(library-config): import std::io in tests submodule

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

Author: morrisonlevi

libdd-library-config/src/otel_process_ctx.rs

@@ -627,6 +627,7 @@ pub mod linux {
     #[cfg(test)]
     #[serial_test::serial]
     mod tests {
+        use std::io;
         use std::sync::atomic::Ordering;
 
         use super::MappingHeader;