feat: add early binary detection and prevent duplicate metadata saving

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

src/meta_plugin/system.rs

@@ -22,6 +22,7 @@ pub struct BinaryMetaPlugin {
     meta_name: String,
     buffer: Vec<u8>,
     max_buffer_size: usize,
+    saved_during_io: bool,
     item_id: Option<i64>,
     conn: Option<*mut Connection>,
 }
@@ -32,6 +33,7 @@ impl BinaryMetaPlugin {
             meta_name: "binary".to_string(),
             buffer: Vec::new(),
             max_buffer_size: 4096, // 4KB
+            saved_during_io: false,
             item_id: None,
             conn: None,
         }
@@ -49,6 +51,12 @@ impl MetaPlugin for BinaryMetaPlugin {
     }
 
     fn finalize(&mut self) -> io::Result<String> {
+        // If we already saved during IO, don't save again
+        if self.saved_during_io {
+            // Return the current value to avoid errors, but it won't be saved again
+            let is_binary = is_binary(&self.buffer);
+            return Ok(if is_binary { "true".to_string() } else { "false".to_string() });
+        }
         let is_binary = is_binary(&self.buffer);
         Ok(if is_binary { "true".to_string() } else { "false".to_string() })
     }