--machine mode flag for verbose CLI output

crates/g3-core/src/ui_writer.rs

@@ -52,6 +52,10 @@ pub trait UiWriter: Send + Sync {
     
     /// Flush any buffered output
     fn flush(&self);
+    
+    /// Returns true if this UI writer wants full, untruncated output
+    /// Default is false (truncate for human readability)
+    fn wants_full_output(&self) -> bool { false }
 }
 
 /// A no-op implementation for when UI output is not needed
@@ -75,4 +79,5 @@ impl UiWriter for NullUiWriter {
     fn print_agent_response(&self, _content: &str) {}
     fn notify_sse_received(&self) {}
     fn flush(&self) {}
+    fn wants_full_output(&self) -> bool { false }
 }