Remove is_tail field from Call node

The `is_tail` field on the `BoundKind::Call` node was an intermediate
representation for tail-call optimization and is no longer needed as a
distinct field. The TCO pass now embeds this information directly into
the `RuntimeMetadata` of the `ExecNode`, which is the VM's internal AST.
This simplifies the `BoundKind::Call` structure and removes redundant
information.

src/ast/compiler/dumper.rs

@@ -137,9 +137,8 @@ impl Dumper {
                 self.log(&format!("Parameter (Name: '{}', Slot: {})", name.name, slot), node);
             }
 
-            BoundKind::Call { callee, args, is_tail } => {
-                let label = if *is_tail { "Call (TCO)" } else { "Call" };
-                self.log(label, node);
+            BoundKind::Call { callee, args } => {
+                self.log("Call", node);
                 self.indent += 1;
                 
                 self.write_indent();