feat: add multi file support, Implement parser context queue and external symbol registration

.gitignore

@@ -39,3 +39,6 @@ external/
 !CHANGELOG.md
 *.vsix
 editors/vscode/package-lock.json
+
+# Local build artifacts
+/refcell_eq

core/ast/src/lib.rs

@@ -31,7 +31,7 @@
 //! - [`arena::Arena`] - Central storage for all AST nodes with O(1) lookups
 //! - [`builder::Builder`] - Builds AST from tree-sitter concrete syntax tree
 //! - [`nodes`] - AST node type definitions (`SourceFile`, `FunctionDefinition`, etc.)
-//! - [`parser_context::ParserContext`] - Multi-file parsing context (WIP)
+//! - [`parser_context::ParserContext`] - Multi-file parsing context
 //!
 //! # Key Features
 //!

core/ast/src/nodes.rs

@@ -451,7 +451,7 @@ ast_nodes! {
     pub struct ModuleDefinition {
         pub visibility: Visibility,
         pub name: Rc<Identifier>,
-        pub body: Option<Vec<Definition>>,
+        pub body: RefCell<Option<Vec<Definition>>>,
     }
 
     pub struct Argument {

core/ast/src/nodes_impl.rs

@@ -443,7 +443,7 @@ impl ModuleDefinition {
             location,
             visibility,
             name,
-            body,
+            body: RefCell::new(body),
         }
     }