perf: use targeted AST lookups instead of getExportedDeclarations

Replace sourceFile.getExportedDeclarations() (which resolves all exports
and forces type checker work) with targeted lookups:
- getExportAssignment() for default exports
- getVariableDeclaration(name) for named exports

~10% improvement in lazy mode (9.06s -> 8.12s on real monorepo).

Author: Alp

src/cli/config.ts

@@ -87,13 +87,18 @@ export function getZeroSchemaDefsFromConfig({
     );
   }
 
-  const exportDeclarations = sourceFile.getExportedDeclarations();
-
-  for (const [name, declarations] of exportDeclarations.entries()) {
-    for (const declaration of declarations) {
-      if (exportName === name) {
-        return [name, declaration] as const;
-      }
+  // Targeted lookup avoids getExportedDeclarations() which forces full type resolution
+  if (exportName === 'default') {
+    const exportAssignment = sourceFile.getExportAssignment(
+      d => !d.isExportEquals(),
+    );
+    if (exportAssignment) {
+      return [exportName, exportAssignment] as const;
+    }
+  } else {
+    const variableDeclaration = sourceFile.getVariableDeclaration(exportName);
+    if (variableDeclaration) {
+      return [exportName, variableDeclaration] as const;
     }
   }