feat: Add tail call optimization

Introduce a TCO pass to the compiler and modify the VM to handle tail
calls.
This allows for deep recursion without stack overflow.

src/ast/types.rs

@@ -70,6 +70,7 @@ pub enum Value {
     Function(Rc<dyn Fn(Vec<Value>) -> Value>),
     Object(Rc<dyn Object>), // For compiled Closures and other opaque types
     Cell(Rc<RefCell<Value>>), // Boxed value for captures
+    TailCallRequest(Rc<dyn Object>, Vec<Value>), // Internal: For TCO
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
@@ -113,6 +114,7 @@ impl Value {
             Value::Function { .. } => StaticType::Any, // Dynamic function
             Value::Object(o) => StaticType::Object(o.type_name()),
             Value::Cell(c) => c.borrow().static_type(),
+            Value::TailCallRequest(_, _) => panic!("Internal VM state leaked: TailCallRequest"),
         }
     }
 }
@@ -147,6 +149,7 @@ impl fmt::Display for Value {
             Value::Function(_) => write!(f, "<native fn>"),
             Value::Object(o) => write!(f, "<{}>", o.type_name()),
             Value::Cell(c) => write!(f, "{}", c.borrow()),
+            Value::TailCallRequest(_, _) => panic!("Internal VM state leaked: TailCallRequest"),
         }
     }
 }