- Fix _providerFromModelValue and _getOptionProviderId to correctly parse
@custom:<slug>:<model> format (non-greedy, stops at first colon after @custom:)
- This prevents truncation of colon-bearing model IDs like model-a:free
- The restore path (_isSelectedModelRow) now correctly matches the row
because the provider is parsed correctly
- Related: #6884, #6895, #6221 re-gate