fix(sidebar): verify folder deletion against the backend

The sidebar derives "empty folder" from the models-only list, which omits
models flagged `exclude: true`, while the delete guard walks the folder on
disk and refuses on any weight file. A folder whose models are all excluded
therefore looked empty, offered the confirmation, and then failed with
"still contains models".

The delete modal still opens on that prediction, but is now corrected by a
dry run of the very delete the user is about to confirm, so the button state
cannot contradict the backend. The confirm button stays disabled while the
check runs, and a late answer is discarded once the modal is dismissed or
retargeted. The dry run also covers weight files no scanner indexes (a lora
folder holding only a `.gguf`, say) and files that appeared after the last
scan.

`_collect_folder_manifest()` now reports `excluded_model_count`, and the
refusal names the excluded models, so the message explains the mismatch
instead of reading like a bug. Locale files carry the sync placeholders in
this commit; the translations follow.

tests/frontend/components/sidebarManager.folderManagement.test.js

@@ -631,24 +631,38 @@ describe('SidebarManager folder deletion', () => {
     vi.clearAllMocks();
   });
 
-  it('opens the confirm state for a folder whose subtree holds no models', () => {
-    const manager = createManager(createApiClient());
+  it('opens the confirm state for a folder whose subtree holds no models', async () => {
+    const apiClient = createApiClient();
+    const manager = createManager(apiClient);
     manager.nonEmptyFolders = new Set(['', 'full']);
 
-    manager.showDeleteFolderModal('empty');
+    await manager.showDeleteFolderModal('empty');
 
     const modal = document.getElementById('deleteFolderModal');
     expect(modal.dataset.state).toBe('confirm');
     expect(confirmBtn().style.display).toBe('');
+    expect(confirmBtn().disabled).toBe(false);
     expect(manager._pendingDeleteFolderPath).toBe('empty');
     expect(modalManager.showModal).toHaveBeenCalledWith('deleteFolderModal');
+    // The prediction is confirmed against the real guard before the user can
+    // act on it.
+    expect(apiClient.deleteFolder).toHaveBeenCalledWith(
+      '/models/loras/empty', { dryRun: true }
+    );
   });
 
-  it('explains the refusal when the subtree still holds models', () => {
-    const manager = createManager(createApiClient());
+  it('explains the refusal when the subtree still holds models', async () => {
+    const conflict = Object.assign(new Error('still contains models'), {
+      code: 'not_empty',
+      manifest: { model_count: 2, excluded_model_count: 0 },
+    });
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn().mockRejectedValue(conflict),
+    });
+    const manager = createManager(apiClient);
     manager.nonEmptyFolders = new Set(['', 'full']);
 
-    manager.showDeleteFolderModal('full');
+    await manager.showDeleteFolderModal('full');
 
     const modal = document.getElementById('deleteFolderModal');
     expect(modal.dataset.state).toBe('blocked');
@@ -656,17 +670,134 @@ describe('SidebarManager folder deletion', () => {
     expect(manager._pendingDeleteFolderPath).toBeNull();
   });
 
-  it('treats an unknown folder as model-free when the models-only set is missing', () => {
-    // nonEmptyFolders is null outside the include-empty tree; the server still
-    // refuses a non-empty folder, so the client falls back to the confirm state.
+  it('treats an unknown folder as model-free when the models-only set is missing', async () => {
+    // nonEmptyFolders is null outside the include-empty tree; the dry run is
+    // what actually decides, so the prediction is only a starting point.
     const manager = createManager(createApiClient());
     manager.nonEmptyFolders = null;
 
-    manager.showDeleteFolderModal('empty');
+    await manager.showDeleteFolderModal('empty');
 
     expect(document.getElementById('deleteFolderModal').dataset.state).toBe('confirm');
   });
 
+  it('blocks a folder the tree shows as empty when only excluded models live there', async () => {
+    // The reported mismatch: excluded models are absent from the models-only
+    // set (so the node dims as empty), yet they are real weight files on disk
+    // and the delete guard refuses to cascade over them.
+    const conflict = Object.assign(
+      new Error('Folder still contains 3 model file(s), all excluded from the library'),
+      { code: 'not_empty', manifest: { model_count: 3, excluded_model_count: 3 } }
+    );
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn().mockRejectedValue(conflict),
+    });
+    const manager = createManager(apiClient);
+    manager.nonEmptyFolders = new Set(['', 'full']);
+
+    await manager.showDeleteFolderModal('Flux.1 D/test');
+
+    const modal = document.getElementById('deleteFolderModal');
+    expect(modal.dataset.state).toBe('blocked');
+    expect(confirmBtn().style.display).toBe('none');
+    expect(manager._pendingDeleteFolderPath).toBeNull();
+    // The message names the excluded models instead of contradicting the tree.
+    expect(modal.querySelector('[data-role="message"]').textContent)
+      .toContain('excluded from the library');
+    expect(apiClient.deleteFolder).toHaveBeenCalledWith(
+      '/models/loras/Flux.1 D/test', { dryRun: true }
+    );
+  });
+
+  it('reports how many model files block the delete when some are excluded', async () => {
+    const conflict = Object.assign(new Error('still contains models'), {
+      code: 'not_empty',
+      manifest: { model_count: 4, excluded_model_count: 1 },
+    });
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn().mockRejectedValue(conflict),
+    });
+    const manager = createManager(apiClient);
+    manager.nonEmptyFolders = new Set(['', 'full']);
+
+    await manager.showDeleteFolderModal('mixed');
+
+    expect(
+      document.getElementById('deleteFolderModal')
+        .querySelector('[data-role="message"]').textContent
+    ).toContain('4 model file(s)');
+  });
+
+  it('blocks the delete while a staged delete is still pending', async () => {
+    const busy = Object.assign(new Error('staged delete pending'), { code: 'busy' });
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn().mockRejectedValue(busy),
+    });
+    const manager = createManager(apiClient);
+    manager.nonEmptyFolders = new Set(['', 'full']);
+
+    await manager.showDeleteFolderModal('empty');
+
+    const modal = document.getElementById('deleteFolderModal');
+    expect(modal.dataset.state).toBe('busy');
+    expect(confirmBtn().style.display).toBe('none');
+  });
+
+  it('keeps the confirm button disabled until the check settles', async () => {
+    let release;
+    const apiClient = createApiClient({
+      fetchModelRoots: vi.fn(() => new Promise((resolve) => { release = resolve; })),
+    });
+    const manager = createManager(apiClient);
+    manager.nonEmptyFolders = new Set(['', 'full']);
+
+    const pending = manager.showDeleteFolderModal('empty');
+    expect(confirmBtn().disabled).toBe(true);
+
+    release({ roots: ['/models/loras'] });
+    await pending;
+
+    expect(confirmBtn().disabled).toBe(false);
+    expect(document.getElementById('deleteFolderModal').dataset.state).toBe('confirm');
+  });
+
+  it('ignores a dry-run answer that lands after the modal was dismissed', async () => {
+    let rejectProbe;
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn(() => new Promise((_resolve, reject) => { rejectProbe = reject; })),
+    });
+    const manager = createManager(apiClient);
+    manager.nonEmptyFolders = new Set(['', 'full']);
+
+    const pending = manager.showDeleteFolderModal('empty');
+    expect(document.getElementById('deleteFolderModal').dataset.state).toBe('confirm');
+
+    await vi.waitFor(() => expect(rejectProbe).toBeTypeOf('function'));
+
+    manager.hideDeleteFolderModal();
+    rejectProbe(Object.assign(new Error('still contains models'), {
+      code: 'not_empty',
+      manifest: { model_count: 1, excluded_model_count: 0 },
+    }));
+    await pending;
+
+    expect(document.getElementById('deleteFolderModal').dataset.state).toBe('confirm');
+  });
+
+  it('falls back to the tree prediction when the check fails for another reason', async () => {
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn().mockRejectedValue(new Error('network down')),
+    });
+    const manager = createManager(apiClient);
+    manager.nonEmptyFolders = new Set(['', 'full']);
+
+    await manager.showDeleteFolderModal('empty');
+
+    const modal = document.getElementById('deleteFolderModal');
+    expect(modal.dataset.state).toBe('confirm');
+    expect(confirmBtn().disabled).toBe(false);
+  });
+
   it('deletes the folder and offers the undo affordance for an empty one', async () => {
     const apiClient = createApiClient();
     const manager = createManager(apiClient);
@@ -732,6 +863,25 @@ describe('SidebarManager folder deletion', () => {
     expect(manager.refresh).not.toHaveBeenCalled();
   });
 
+  it('includes the model count in the stale-tree toast when the manifest has one', async () => {
+    const conflict = Object.assign(new Error('still contains models'), {
+      code: 'not_empty',
+      manifest: { model_count: 3, excluded_model_count: 3 },
+    });
+    const apiClient = createApiClient({
+      deleteFolder: vi.fn().mockRejectedValue(conflict),
+    });
+    const manager = createManager(apiClient);
+    manager.refresh = vi.fn().mockResolvedValue(undefined);
+
+    const success = await manager._deleteFolder('full');
+
+    expect(success).toBe(false);
+    expect(showToast).toHaveBeenCalledWith(
+      'sidebar.deleteFolderResult.notEmptyWithCount', { count: 3 }, 'warning'
+    );
+  });
+
   it('surfaces a busy folder with a staged delete', async () => {
     const busy = Object.assign(new Error('staged delete pending'), { code: 'busy' });
     const apiClient = createApiClient({