Add 'again' keyword for recursive calls

The `again` keyword is introduced to facilitate explicit recursive
function calls.
It is restricted to tail-call positions to prevent dead code and ensure
TCO
optimization. Type checking is enhanced to validate argument types
against
function parameters.

src/ast/compiler/dumper.rs

@@ -187,6 +187,13 @@ impl Dumper {
                 self.indent -= 1;
             }
 
+            BoundKind::Again { args } => {
+                self.log("Again", node);
+                self.indent += 1;
+                self.visit(args);
+                self.indent -= 1;
+            }
+
             BoundKind::Block { exprs } => {
                 self.log("Block", node);
                 self.indent += 1;