fix: adjust binary detection threshold to properly classify random data as binary

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

src/meta_plugin/system.rs

@@ -72,7 +72,7 @@ impl BinaryMetaPlugin {
         }
         
         // Final fallback: check printable character ratio
-        Self::calculate_printable_ratio(data) < 0.3
+        Self::calculate_printable_ratio(data) < 0.7
     }
     
     /// Check for known binary file signatures