Refactor: Implement Record Layouts and Optimized Field Access

Introduces a new `RecordLayout` system for efficient and type-safe
record handling.

Key changes:
- `RecordLayout` struct with `O(1)` field lookup using FMap
  optimization.
- Field accessors (`.name`) are now first-class callable values.
- Parser recognizes dot-prefixed identifiers as field accessors.
- Binder and TypeChecker handle field accessors.
- Optimizer transforms field accessor calls into specialized `GetField`
  nodes.
- VM executes `GetField` efficiently by directly accessing record
  values.
- Adds a new `records.myc` example showcasing record features.
- Improves comparison logic for records to use pointer equality for
  layout.

src/ast/nodes.rs

@@ -65,6 +65,8 @@ pub enum UntypedKind {
     Constant(Value),
     Identifier(Symbol),
     Parameter(Symbol),
+    /// A first-class field accessor (e.g. .name)
+    FieldAccessor(crate::ast::types::Keyword),
     If {
         cond: Box<Node<UntypedKind>>,
         then_br: Box<Node<UntypedKind>>,