feat(embedding): send embedding to workflow + fix copy button format

- Fix copy button on embedding cards to copy 'embedding:folder/name' format
- Add send-embedding-to-workflow for Prompt (LoraManager), Text (LoraManager),
  and CLIPTextEncode nodes, appending embedding code to text content
- Extend workflow registry to register text-capable nodes by comfyClass
  (not generic widget name 'text') to avoid false matches
- Add mode parameter to update_node_widget API/event for append support
- Fix single/bulk context menus: single shows plain 'Send to Workflow',
  bulk collapses submenu into direct action for embeddings (append-only)

templates/embeddings.html

@@ -16,6 +16,7 @@
     <div class="context-menu-separator menu-section-break"></div>
     <!-- Workflow -->
     <div class="context-menu-item" data-action="copyname"><i class="fas fa-copy"></i> {{ t('loras.contextMenu.copyFilename') }}</div>
+    <div class="context-menu-item" data-action="sendtoworkflow"><i class="fas fa-paper-plane"></i> {{ t('checkpoints.contextMenu.sendToWorkflow') }}</div>
     <div class="context-menu-separator menu-section-break"></div>
     <!-- Media / Preview -->
     <div class="context-menu-item" data-action="preview"><i class="fas fa-folder-open"></i> {{ t('loras.contextMenu.openExamples') }}</div>