fix: Address minor issues in module system implementation

- Fix unused variable warning in src/parser/helpers.rs:252 with #[allow(unused_variables)]
- Improve documentation in type checker for include statement limitations
- Add detailed comment explaining current type checking behavior and future improvements

Co-authored-by: logbie <logbie@users.noreply.github.com>

Author: claude[bot]

src/parser/helpers.rs

@@ -249,6 +249,7 @@ impl<'a> Parser<'a> {
                 }
                 Token::KeywordEnd => {
                     // Handle orphaned "end" tokens during error recovery
+                    #[allow(unused_variables)]
                     let line = token.line;
                     exec_trace!("Synchronizing: found 'end' token at line {}", line);
                     self.bump_sync();

src/typechecker/mod.rs

@@ -1688,7 +1688,10 @@ impl TypeChecker {
                     );
                 }
                 // Note: Include statements execute in parent scope, making their symbols available
-                // Full symbol resolution would require parsing the included file during type checking
+                // at runtime. However, the type checker doesn't currently parse included files,
+                // which can result in false "not found" errors for symbols defined in included files.
+                // Future improvement: Parse and analyze included files during type checking
+                // to register their symbols in the current scope for more accurate diagnostics.
             }
 
             Statement::ExportStatement {