Replace the generic "Invalid variable" message in prompt editor variable
labels with two context-aware messages: one for missing nodes and another
for uninstalled model plugins. Add useLlmModelPluginInstalled hook that
checks LLM node model providers against installed providers via
useProviderContextSelector. Migrate Tooltip usage to base-ui primitives
and replace RiErrorWarningFill with Warning icon in warning color.
1abbaf9fd5