refactor: Simplify streaming content API to use a single filter option

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

src/services/async_item_service.rs

@@ -307,15 +307,7 @@ impl AsyncItemService {
     pub async fn get_item_content_info_streaming(
         &self,
         item_id: i64,
-        head_bytes: Option<usize>,
-        head_words: Option<usize>,
-        head_lines: Option<usize>,
-        tail_bytes: Option<usize>,
-        tail_words: Option<usize>,
-        tail_lines: Option<usize>,
-        line_start: Option<usize>,
-        line_end: Option<usize>,
-        grep: Option<String>,
+        filter: Option<String>,
     ) -> Result<(Box<dyn Read + Send>, String, bool), CoreError> {
         let db = self.db.clone();
         let item_service = self.item_service.clone();
@@ -325,7 +317,7 @@ impl AsyncItemService {
             item_service.get_item_content_info_streaming(
                 &conn, 
                 item_id, 
-                None
+                filter
             )
         })
         .await