Refactor: Use generic Define bound kind

This commit consolidates `DefLocal` and `DefGlobal` into a single
`Define` bound kind. This simplifies the AST and makes it more
consistent.

It also introduces `DeclarationKind` to differentiate between variable
and parameter definitions.

src/ast/compiler/lambda_collector.rs

@@ -22,13 +22,11 @@ impl<'a, T: Clone> LambdaCollector<'a, T> {
                 }
             }
 
-            BoundKind::DefGlobal {
-                global_index,
-                value,
-                ..
-            } => {
-                // Register the full Lambda node as the template.
-                if let BoundKind::Lambda { .. } = &value.kind {
+            BoundKind::Define { addr, value, .. } => {
+                // Register global function definitions (lambdas)
+                if let Address::Global(global_index) = addr
+                    && let BoundKind::Lambda { .. } = &value.kind
+                {
                     self.registry
                         .insert(*global_index, (*value).as_ref().clone());
                 }
@@ -63,10 +61,6 @@ impl<'a, T: Clone> LambdaCollector<'a, T> {
                 self.visit(body);
             }
 
-            BoundKind::DefLocal { value, .. } => {
-                self.visit(value);
-            }
-
             BoundKind::Call { callee, args } => {
                 self.visit(callee);
                 self.visit(args);