fix: remove duplicate metadata processing in MagicFileMetaPlugin

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

src/meta_plugin/magic.rs

@@ -9,7 +9,7 @@ use crate::meta_plugin::MetaPlugin;
 pub struct MagicFileMetaPlugin {
     buffer: Vec<u8>,
     max_buffer_size: usize,
-    is_saved: bool,
+    is_finalized: bool,
     cookie: Option<Cookie>,
     base: crate::meta_plugin::BaseMetaPlugin,
 }
@@ -51,7 +51,7 @@ impl MagicFileMetaPlugin {
         MagicFileMetaPlugin {
             buffer: Vec::new(),
             max_buffer_size,
-            is_saved: false,
+            is_finalized: false,
             cookie: None,
             base,
         }
@@ -119,6 +119,13 @@ impl MagicFileMetaPlugin {
 }
 
 impl MetaPlugin for MagicFileMetaPlugin {
+    fn is_finalized(&self) -> bool {
+        self.is_finalized
+    }
+    
+    fn set_finalized(&mut self, finalized: bool) {
+        self.is_finalized = finalized;
+    }
     
     fn initialize(&mut self) -> crate::meta_plugin::MetaPluginResponse {
         // Initialize the magic cookie once
@@ -146,7 +153,18 @@ impl MetaPlugin for MagicFileMetaPlugin {
     }
 
     fn finalize(&mut self) -> crate::meta_plugin::MetaPluginResponse {
+        // If already finalized, don't process again
+        if self.is_finalized {
+            return crate::meta_plugin::MetaPluginResponse {
+                metadata: Vec::new(),
+                is_finalized: true,
+            };
+        }
+        
         let metadata = self.process_magic_types();
+        
+        // Mark as finalized
+        self.is_finalized = true;
 
         crate::meta_plugin::MetaPluginResponse {
             metadata,
@@ -155,6 +173,14 @@ impl MetaPlugin for MagicFileMetaPlugin {
     }
 
     fn update(&mut self, data: &[u8]) -> crate::meta_plugin::MetaPluginResponse {
+        // If already finalized, don't process more data
+        if self.is_finalized {
+            return crate::meta_plugin::MetaPluginResponse {
+                metadata: Vec::new(),
+                is_finalized: true,
+            };
+        }
+        
         let mut metadata = Vec::new();
 
         // Only collect up to max_buffer_size
@@ -166,6 +192,9 @@ impl MetaPlugin for MagicFileMetaPlugin {
             // Check if we've reached our buffer limit and return metadata
             if self.buffer.len() >= self.max_buffer_size {
                 metadata = self.process_magic_types();
+                
+                // Mark as finalized when we've processed enough data
+                self.is_finalized = true;
             }
         }