feat: Implement AST macros and templates

This commit introduces support for AST macros and templates, enabling
users to define and use custom, reusable components within the visual
DSL.

Key changes include:
- A new `MacroRegistry` to manage macro definitions.
- A `MacroExpander` to process macro calls and expand templates.
- A `MacroEvaluator` trait for evaluating expressions during expansion.
- The `Expansion` node in `BoundKind` to preserve the original macro
  call and its expanded form for debugging.
- Updates to the `Binder`, `Dumper`, and `UpvalueAnalyzer` to handle the
  new macro constructs.
- New examples demonstrating various macro functionalities like
  `unless`, splicing, and nested macros.

src/ast/compiler/bound_nodes.rs

@@ -70,6 +70,13 @@ pub enum BoundKind {
     Map {
         entries: Vec<(Node<BoundKind, StaticType>, Node<BoundKind, StaticType>)>,
     },
+    /// An expanded macro call, preserving the original call for debugging and UI.
+    Expansion {
+        /// The original call from the untyped AST.
+        original_call: Rc<Node<crate::ast::nodes::UntypedKind>>,
+        /// The result of binding the expanded AST.
+        bound_expanded: Box<Node<BoundKind, StaticType>>,
+    },
 }
 
 impl BoundKind {
@@ -88,6 +95,7 @@ impl BoundKind {
             BoundKind::Block { .. } => "BLOCK".to_string(),
             BoundKind::Tuple { elements } => format!("TUPLE({})", elements.len()),
             BoundKind::Map { entries } => format!("MAP({})", entries.len()),
+            BoundKind::Expansion { .. } => "EXPANSION".to_string(),
         }
     }
 }