Refactor: Migrate to clap for CLI argument parsing

The project now uses the `clap` crate for handling command-line
arguments, replacing the previous manual parsing approach. This includes
adding `clap` as a dependency and creating a `Cli` struct to define the
command-line interface. The `main` function has been updated to parse
these arguments and handle file input or direct script evaluation.

src/bin/ast.rs

@@ -0,0 +1,45 @@
+use myc::ast::environment::Environment;
+use clap::Parser;
+use std::fs;
+use std::path::PathBuf;
+
+#[derive(Parser)]
+#[command(author, version, about = "MYC AST Compiler CLI", long_about = None)]
+struct Cli {
+    /// The script file to run
+    #[arg(value_name = "FILE")]
+    file: Option<PathBuf>,
+
+    /// Run a script string directly
+    #[arg(short, long)]
+    eval: Option<String>,
+}
+
+fn main() {
+    let cli = Cli::parse();
+    let env = Environment::new();
+
+    if let Some(script_str) = cli.eval {
+        execute(&env, &script_str);
+    } else if let Some(file_path) = cli.file {
+        match fs::read_to_string(&file_path) {
+            Ok(content) => execute(&env, &content),
+            Err(e) => {
+                eprintln!("Error reading file {:?}: {}", file_path, e);
+                std::process::exit(1);
+            }
+        }
+    } else {
+        println!("MYC AST Compiler CLI. Use --help for usage.");
+    }
+}
+
+fn execute(env: &Environment, source: &str) {
+    match env.run_script(source) {
+        Ok(result) => println!("{}", result),
+        Err(e) => {
+            eprintln!("Error: {}", e);
+            std::process::exit(1);
+        }
+    }
+}

src/lib.rs

@@ -0,0 +1,4 @@
+pub mod ast;
+
+#[cfg(test)]
+mod integration_test;

src/main.rs

@@ -1,9 +1,5 @@
 use eframe::egui;
-use crate::ast::environment::Environment;
-
-pub mod ast;
-#[cfg(test)]
-mod integration_test;
+use myc::ast::environment::Environment;
 
 fn main() -> eframe::Result {
     let options = eframe::NativeOptions {