fix: remove unused parameter prefixes and update tail filter implementation

Co-authored-by: aider (openai/andrew/openrouter/deepseek/deepseek-chat-v3.1) <aider@aider.chat>

src/services/item_service.rs

@@ -147,13 +147,13 @@ impl ItemService {
         conn: &Connection,
         id: i64,
         head_bytes: Option<usize>,
-        _head_words: Option<usize>,
+        head_words: Option<usize>,
         head_lines: Option<usize>,
         tail_bytes: Option<usize>,
-        _tail_words: Option<usize>,
+        tail_words: Option<usize>,
         tail_lines: Option<usize>,
-        _line_start: Option<usize>,
-        _line_end: Option<usize>,
+        line_start: Option<usize>,
+        line_end: Option<usize>,
         grep: Option<String>,
     ) -> Result<(Vec<u8>, String, bool), CoreError> {
         // Use streaming approach to handle all filtering options consistently