feat: optimize item content retrieval to reduce redundant database queries

Co-authored-by: aider (openai/andrew/openrouter/qwen/qwen3-coder) <aider@aider.chat>

src/modes/server/api/item.rs

@@ -168,6 +168,7 @@ pub async fn handle_get_item_latest_content(
 
     let item_service = AsyncItemService::new(state.data_dir.clone(), state.db.clone());
 
+    // First get the item metadata to check if it's binary and get MIME type
     let item_with_meta = item_service
         .find_item(vec![], tags, HashMap::new())
         .await;
@@ -175,8 +176,37 @@ pub async fn handle_get_item_latest_content(
     match item_with_meta {
         Ok(item) => {
             let item_id = item.item.id.unwrap();
-            match item_service.stream_item_content_by_id(item_id, params.allow_binary, params.offset, params.length).await {
+            let metadata = item.meta_as_map();
-                Ok((stream, mime_type)) => {
+            let mime_type = metadata
+                .get("mime_type")
+                .map(|s| s.to_string())
+                .unwrap_or_else(|| "application/octet-stream".to_string());
+            
+            // Check if content is binary when allow_binary is false
+            if !params.allow_binary {
+                let is_content_binary = if let Some(binary_val) = metadata.get("binary") {
+                    binary_val == "true"
+                } else {
+                    // For the binary check, we need to read a sample of the content
+                    match item_service.get_item_content(item_id).await {
+                        Ok(item_with_content) => {
+                            crate::common::is_binary::is_binary(&item_with_content.content)
+                        }
+                        Err(e) => {
+                            warn!("Failed to get content for binary check for item {}: {}", item_id, e);
+                            return Err(StatusCode::INTERNAL_SERVER_ERROR);
+                        }
+                    }
+                };
+                
+                if is_content_binary {
+                    return Err(StatusCode::BAD_REQUEST);
+                }
+            }
+            
+            // Now stream the content with the specified offset and length
+            match item_service.stream_item_content_by_id(item_id, true, params.offset, params.length).await {
+                Ok((stream, _)) => {
                     let body = axum::body::Body::from_stream(stream);
                     let response = Response::builder()
                         .header(header::CONTENT_TYPE, mime_type)