docs: Add Rustdoc comments to CompressionService methods

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

src/services/compression_service.rs

@@ -7,11 +7,56 @@ use anyhow::anyhow;
 
 pub struct CompressionService;
 
+/// Service for handling compression and decompression of item content.
+///
+/// Provides methods to read compressed item files either fully into memory
+/// or as streaming readers. Supports various compression types via engines.
+///
+/// # Examples
+///
+/// ```
+/// let service = CompressionService::new();
+/// let content = service.get_item_content(path, "gzip")?;
+/// ```
+
 impl CompressionService {
+    /// Creates a new CompressionService instance.
+    ///
+    /// # Returns
+    ///
+    /// A new `CompressionService`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let service = CompressionService::new();
+    /// ```
     pub fn new() -> Self {
         Self
     }
 
+    /// Reads and decompresses the full content of an item file into memory.
+    ///
+    /// # Arguments
+    ///
+    /// * `item_path` - Path to the compressed item file.
+    /// * `compression` - Compression type string (e.g., "gzip").
+    ///
+    /// # Returns
+    ///
+    /// * `Result<Vec<u8>, CoreError>` - Decompressed content bytes.
+    ///
+    /// # Errors
+    ///
+    /// * `CoreError::Compression(...)` - If compression type invalid.
+    /// * `CoreError::Other(...)` - If file open or read fails.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let content = service.get_item_content(item_path, "lz4")?;
+    /// assert_eq!(content.len(), expected_size);
+    /// ```
     pub fn get_item_content(&self, item_path: PathBuf, compression: &str) -> Result<Vec<u8>, CoreError> {
         let compression_type = CompressionType::from_str(compression)
             .map_err(|e| CoreError::Compression(e.to_string()))?;
@@ -25,6 +70,32 @@ impl CompressionService {
         Ok(content)
     }
 
+    /// Opens a streaming reader for decompressing item content.
+    ///
+    /// For Send compatibility, reads full content into memory and returns a Cursor.
+    /// Note: Not suitable for very large files due to memory usage.
+    ///
+    /// # Arguments
+    ///
+    /// * `item_path` - Path to the compressed item file.
+    /// * `compression` - Compression type string.
+    ///
+    /// # Returns
+    ///
+    /// * `Result<Box<dyn Read + Send>, CoreError>` - Boxed streaming reader.
+    ///
+    /// # Errors
+    ///
+    /// * `CoreError::Compression(...)` - If compression type invalid.
+    /// * `CoreError::Other(...)` - If file open or read fails.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// let mut reader = service.stream_item_content(item_path, "gzip")?;
+    /// let mut buf = [0; 1024];
+    /// let n = reader.read(&mut buf)?;
+    /// ```
     pub fn stream_item_content(
         &self,
         item_path: PathBuf,