Add missing unit tests for AI Assistant

[nicOwlas]

Backend

• ai-assistant.resolver
  • Mock HuggingFace and IOG fetch queries and cover the runAiAssistant mutation.

Frontend

• SearchInput
  • Value I/O
  • Clear button shown/hidden
  • Clear button clears the text
• ComboBox
  • Mouse usage
  • Keyboard usage
  • Search correctly filtering
  • Search is empty when opened
• undo-store/run-ai-assistant.effect.ts -> mock as with the other effects
• labeling-tool/options-tool-bar/ai-assistant-toolbar.tsx -> Should cover the typical high-level relations and actions. For example, the "post-process with auto-polygon" action should be enabled only if the selected AiAssistant output is a Box.