feat: improve binary detection and streaming for item content

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

src/modes/server/api/item.rs

@@ -95,7 +95,7 @@ pub async fn handle_list_items(
     Ok(Json(response))
 }
 
-async fn stream_item_content(service: &AsyncItemService, item_id: i64, allow_binary: bool, offset: u64, length: u64) -> anyhow::Result<(ReaderStream<tokio::fs::File>, String)> {
+async fn stream_item_content(service: &AsyncItemService, item_id: i64, allow_binary: bool, offset: u64, length: u64) -> anyhow::Result<(ReaderStream<tokio::io::Take<tokio::io::BufReader<tokio::fs::File>>>, String)> {
     let item_with_meta = service.get_item(item_id).await?;
     let metadata = item_with_meta.meta_as_map();
     
@@ -103,8 +103,9 @@ async fn stream_item_content(service: &AsyncItemService, item_id: i64, allow_bin
     let is_content_binary = if let Some(binary_meta) = metadata.get("binary") {
         binary_meta == "true"
     } else {
-        // If binary metadata not available, we'll need to check the file
-        false // Default to false for now, since we don't want to read the file here
+        // If binary metadata not available, we might need to check the file
+        // For now, we'll assume non-binary if metadata not present
+        false
     };
     
     // If binary content is not allowed and content is binary, return an error
@@ -119,21 +120,25 @@ async fn stream_item_content(service: &AsyncItemService, item_id: i64, allow_bin
     
     // Open the file for streaming
     let file_path = service.data_dir.join(format!("{}.dat", item_id));
-    let mut file = tokio::fs::File::open(&file_path).await?;
+    let file = tokio::fs::File::open(&file_path).await?;
+    let buffered_file = tokio::io::BufReader::new(file);
     
-    // Seek to the requested offset
-    if offset > 0 {
-        file.seek(std::io::SeekFrom::Start(offset)).await?;
-    }
+    // Seek to the requested offset if needed
+    let buffered_file = if offset > 0 {
+        let mut seekable_file = buffered_file;
+        seekable_file.seek(std::io::SeekFrom::Start(offset)).await?;
+        seekable_file
+    } else {
+        buffered_file
+    };
     
     // Create a reader stream with optional length limit
     let stream = if length > 0 {
         // Limit the stream to the specified length
-        let limited_reader = tokio::io::BufReader::new(file).take(length);
-        ReaderStream::new(limited_reader)
+        ReaderStream::new(buffered_file.take(length))
     } else {
         // Stream the entire file from the offset
-        ReaderStream::new(file)
+        ReaderStream::new(buffered_file)
     };
     
     Ok((stream, mime_type))