Add is_first_frame flag to CompilerApp

Introduces a new `is_first_frame` boolean flag to the `CompilerApp`
struct to manage initial UI state, specifically for requesting focus on
the source code editor on the first frame. This commit also moves the
compilation logic into a dedicated `compile` method for better
organization and introduces a Shift+Enter keyboard shortcut for
compilation.

src/main.rs

@@ -19,6 +19,7 @@ struct CompilerApp {
     source_code: String,
     output_log: String,
     env: Environment,
+    is_first_frame: bool,
 }
 
 impl Default for CompilerApp {
@@ -27,6 +28,24 @@ impl Default for CompilerApp {
             source_code: String::new(),
             output_log: String::from("Ready to compile..."),
             env: Environment::new(),
+            is_first_frame: true,
+        }
+    }
+}
+
+impl CompilerApp {
+    fn compile(&mut self) {
+        match self.env.run_script(&self.source_code) {
+            Ok(result) => {
+                self.output_log = format!(
+                    "Execution Successful.\nResult: {}\n\nFinished at {:?}",
+                    result,
+                    std::time::SystemTime::now(),
+                );
+            }
+            Err(e) => {
+                self.output_log = format!("Error: {}", e);
+            }
         }
     }
 }
@@ -43,18 +62,7 @@ impl eframe::App for CompilerApp {
 
                 // Compile Button (at the top of the bottom panel)
                 if ui.button("Compile").clicked() {
-                    match self.env.run_script(&self.source_code) {
-                        Ok(result) => {
-                            self.output_log = format!(
-                                "Execution Successful.\nResult: {}\n\nFinished at {:?}",
-                                result,
-                                std::time::SystemTime::now(),
-                            );
-                        }
-                        Err(e) => {
-                            self.output_log = format!("Error: {}", e);
-                        }
-                    }
+                    self.compile();
                 }
 
                 ui.add_space(5.0);
@@ -80,12 +88,27 @@ impl eframe::App for CompilerApp {
             ui.heading("Source Code Editor");
             ui.label("Input Source:");
 
+            let editor_id = ui.id().with("source_code_editor");
+
+            // Handle Shift+Enter shortcut BEFORE the editor handles it
+            let shortcut = egui::KeyboardShortcut::new(egui::Modifiers::SHIFT, egui::Key::Enter);
+            if ui.input_mut(|i| i.consume_shortcut(&shortcut)) {
+                self.compile();
+            }
+
+            // Set initial focus
+            if self.is_first_frame {
+                ui.ctx().memory_mut(|m| m.request_focus(editor_id));
+                self.is_first_frame = false;
+            }
+
             egui::ScrollArea::vertical()
                 .id_salt("source_code_scroll")
                 .show(ui, |ui| {
                     ui.add_sized(
                         ui.available_size(),
                         egui::TextEdit::multiline(&mut self.source_code)
+                            .id(editor_id)
                             .font(egui::TextStyle::Monospace)
                             .desired_width(f32::INFINITY)
                             .lock_focus(true),