Refactor: Simplify type checking context

The type checker's fallback logic for non-lambda nodes was unnecessarily
complex. This commit simplifies it by directly checking the node within
a new, basic type context.

Additionally, the environment now explicitly wraps non-lambda AST nodes
in a lambda before type checking, ensuring consistent handling. This
aligns the type checking process for all top-level expressions.

src/ast/compiler/type_checker.rs

@@ -141,22 +141,8 @@ impl TypeChecker {
                 }
             }
             _ => {
-                // Fallback: Wrap in implicit lambda
-                let virtual_lambda = BoundNode {
-                    identity: node.identity.clone(),
-                    kind: BoundKind::Lambda {
-                        params: Rc::new(Node {
-                            identity: node.identity.clone(),
-                            kind: BoundKind::Tuple { elements: vec![] },
-                            ty: (),
-                        }),
-                        upvalues: vec![],
-                        body: Rc::new(node.clone()),
-                        positional_count: Some(0),
-                    },
-                    ty: (),
-                };
-                self.check(&virtual_lambda, &[], diag)
+                let mut root_ctx = TypeContext::new(0, vec![], &self.global_types, None);
+                self.check_node(node, &mut root_ctx, diag)
             }
         }
     }