Refactor Binder to support recursion and add stdlib operators

This commit introduces two main changes:

1.  **Binder Refactoring**: The `Binder` has been refactored to support
    recursive definitions by pre-declaring names in the scope before
    binding their values. This ensures that a name is visible to itself
    when its definition is being processed.

2.  **Stdlib Operator Implementation**: Several standard library
    operators, including `+`, `-`, `*`, `/`, `>`, and `<`, have been
    implemented. These operators now correctly handle both `Int` and
    `Float` types for numerical operations and comparisons.
    Additionally, the display formatting for `Value::List` and
    `Value::Record` has been improved for better readability. The
    default source code in `main.rs` has also been updated to include a
    Fibonacci example, demonstrating the new recursive capabilities.

src/main.rs

@@ -27,7 +27,25 @@ struct CompilerApp {
 impl Default for CompilerApp {
     fn default() -> Self {
         Self {
-            source_code: String::new(),
+            source_code: String::from(r#"
+(do
+  (def fib (fn [n]
+    (if (< n 2)
+      n
+      (+ (fib (- n 1)) (fib (- n 2))))))
+
+  (def result (fib 10))
+  
+  (def data {
+    :name "Fibonacci"
+    :input 10
+    :output result
+    :sequence [0 1 1 2 3 5 8 13 21 34 55]
+  })
+  
+  data
+)
+"#),
             output_log: String::from("Ready to compile..."),
             env: Environment::new(),
             is_first_frame: true,
@@ -68,8 +86,12 @@ impl eframe::App for CompilerApp {
                 }
 
                 ui.add_space(5.0);
-                ui.separator();
-                ui.label("Output / Logs:");
+                ui.horizontal(|ui| {
+                    ui.label("Output / Logs:");
+                    if ui.button("Copy to Clipboard").clicked() {
+                        ui.ctx().copy_text(self.output_log.clone());
+                    }
+                });
 
                 // Log Output Area
                 egui::ScrollArea::vertical()
@@ -80,7 +102,7 @@ impl eframe::App for CompilerApp {
                             egui::TextEdit::multiline(&mut self.output_log)
                                 .font(egui::TextStyle::Monospace)
                                 .desired_width(f32::INFINITY)
-                                .interactive(false), // Read-only
+                                .interactive(true)
                         );
                     });
             });