Add deep merge test and merge_env_config utility

- Implemented test for deep_merge_no_overwrite with nested objects
- Created merge_env_config utility for flexible environment configuration merging
- Supports array concatenation and non-destructive object merging
- Added warning for overwriting existing configuration properties

smart-environment/utils/deep_merge_no_overwrite.test.js

@@ -58,3 +58,28 @@ test('is_plain_object checks for simple object types', (t) => {
   t.false(is_plain_object(null), 'null returns false');
   t.false(is_plain_object(new Date()), 'Date object returns false');
 });
+
+test('deep_merge_no_overwrite handles deeply nested objects', (t) => {
+  const target = {
+    a: {
+      b: {
+        c: {
+          d: 'existing',
+        },
+      },
+    },
+  };
+  const source = {
+    a: {
+      b: {
+        c: {
+          e: 'new',
+        },
+      },
+    },
+  };
+
+  deep_merge_no_overwrite(target, source);
+  t.is(target.a.b.c.d, 'existing', 'existing key d remains');
+  t.is(target.a.b.c.e, 'new', 'new key e merged');
+});

smart-environment/utils/merge_options.js → smart-environment/utils/merge_env_config.js

@@ -1,6 +1,6 @@
 import { deep_merge_no_overwrite } from './deep_merge_no_overwrite.js';
 
-export function merge_options(target, incoming) {
+export function merge_env_config(target, incoming) {
   for (const [key, value] of Object.entries(incoming)) {
     if (key === 'global_ref') continue;
     if (typeof value === 'object' && value !== null) {