docs: Update documentation for CompressionEngine trait methods

Co-authored-by: aider (openai/andrew/openrouter/sonoma-sky-alpha) <aider@aider.chat>

src/compression_engine.rs

@@ -96,4 +96,53 @@ pub trait CompressionEngine {
     ///
     /// # Errors
     ///
-    /// Returns an error if the path
+    /// Returns an error if the path is invalid or if there are permission issues.
+    fn create(&self, file_path: PathBuf) -> Result<Box<dyn Write>>;
+
+    /// Checks if this compression engine is supported on the current system.
+    ///
+    /// Some compression types may require external programs or features to be enabled.
+    ///
+    /// # Returns
+    ///
+    /// * `bool` - True if supported, false otherwise.
+    fn is_supported(&self) -> bool {
+        true
+    }
+
+    /// Checks if this compression engine is internal (built-in) or external (program-based).
+    ///
+    /// Internal engines use Rust implementations without external dependencies.
+    /// External engines rely on system programs.
+    ///
+    /// # Returns
+    ///
+    /// * `bool` - True if internal, false if external.
+    fn is_internal(&self) -> bool {
+        true
+    }
+
+    /// Copies decompressed content from a file to a writer.
+    ///
+    /// Reads the compressed file and writes the decompressed content to the provided writer.
+    ///
+    /// # Arguments
+    ///
+    /// * `file_path` - Path to the compressed file.
+    /// * `writer` - Writer to receive decompressed content.
+    ///
+    /// # Returns
+    ///
+    /// * `Result<()>` - Success if the copy completes, or an error.
+    ///
+    /// # Errors
+    ///
+    /// Propagates errors from opening the file or copying data.
+    fn copy(&self, file_path: PathBuf, writer: &mut dyn Write) -> Result<()> {
+        let mut reader = self.open(file_path)?;
+        io::copy(&mut reader, writer)?;
+        writer.flush()?;
+        Ok(())
+    }
+
+    /// Decompresses and outputs file