Refactor TUI message formatting: add role label toggle, improve indentation, and adjust role label styling logic. Optimize provider handling.

crates/owlen-core/src/formatting.rs

@@ -30,6 +30,11 @@ impl MessageFormatter {
         self.wrap_width = width.max(20);
     }
 
+    /// Whether role labels should be shown alongside messages
+    pub fn show_role_labels(&self) -> bool {
+        self.show_role_labels
+    }
+
     pub fn format_message(&self, message: &Message) -> Vec<String> {
         // 1) Normalize line breaks to '\n' (handles CR, NEL, LS, PS)
         let normalized: String = message