fix(renderer): drop redundant ternary, add loadChildren idempotence test

src/renderer/stores/file-store.ts

@@ -46,7 +46,7 @@ function entryToNode(entry: FileEntry): FileNode {
     name: entry.name,
     path: entry.path,
     isDirectory: entry.isDirectory,
-    children: entry.isDirectory ? null : null,
+    children: null, // lazy: start unloaded; loadChildren populates this
   };
 }
 
@@ -97,7 +97,7 @@ export const useFileStore = create<FileState>()(
 
       let found = false;
       updateNode(tree, dirPath, (node) => {
-        if (node.loaded) return;
+        if (node.loaded === true) return;
         found = true;
       });
       if (!found) return;

tests/unit/stores/file-store.test.ts

@@ -139,6 +139,28 @@ describe('useFileStore', () => {
     expect(fakeList).not.toHaveBeenCalled();
   });
 
+  it('loadChildren is idempotent: does not re-fetch when already loaded', async () => {
+    fakeList.mockResolvedValue({
+      ok: true,
+      data: [{ name: 'src', path: '/root/src', isDirectory: true }],
+    });
+    await useFileStore.getState().openFolder('/root');
+
+    fakeList.mockClear();
+    fakeList.mockResolvedValue({
+      ok: true,
+      data: [{ name: 'foo.ts', path: '/root/src/foo.ts', isDirectory: false }],
+    });
+
+    await useFileStore.getState().loadChildren('/root/src');
+    const callsAfterFirst = fakeList.mock.calls.length;
+    expect(callsAfterFirst).toBe(1);
+
+    // Second call should be a no-op (loaded is true)
+    await useFileStore.getState().loadChildren('/root/src');
+    expect(fakeList.mock.calls.length).toBe(callsAfterFirst);
+  });
+
   // --- toggleExpanded ---
 
   it('toggleExpanded adds and removes paths from the expanded Set', () => {