fix: update test files to use correct compression engine initialization and add compression_types tests

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/tests/mod.rs

@@ -1,6 +1,8 @@
 #[cfg(test)]
 pub mod compression;
 #[cfg(test)]
+pub mod compression_types;
+#[cfg(test)]
 pub mod compression_engine;
 #[cfg(test)]
 pub mod meta_plugin;