docs: Improve Rustdoc for compression engine, delete mode, and parser modules

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

src/modes/delete.rs

@@ -10,6 +10,11 @@ use rusqlite::Connection;
 
 /// Handles the delete mode: removes items by ID from the database and storage.
 ///
+/// This function processes a list of item IDs, attempting to delete each from
+/// both the database and the underlying file storage. It skips items that are
+/// not found and logs warnings for them. Validation of arguments (e.g., ensuring
+/// IDs are provided and tags are empty) is handled at the clap parsing level.
+///
 /// # Arguments
 ///
 /// * `_cmd` - Clap command for error handling (unused).
@@ -22,7 +27,23 @@ use rusqlite::Connection;
 ///
 /// # Returns
 ///
-/// `Result<()>` on success, or an error if deletion fails.
+/// `Result<()>` on success, or an error if deletion fails for any item.
+///
+/// # Errors
+///
+/// Returns an `anyhow::Error` if a deletion operation fails due to database
+/// or I/O issues (excluding `ItemNotFound`, which is handled gracefully).
+///
+/// # Examples
+///
+/// ```
+/// // This would be called from main after parsing args
+/// mode_delete(&mut cmd, &settings, &config, &mut vec![1, 2], &mut vec![], &mut conn, data_path)?;
+/// ```
+///
+/// # Panics
+///
+/// None.
 pub fn mode_delete(
     _cmd: &mut Command,
     _settings: &config::Settings,