Remove force parameter parsing and passing from _fetch_index method in PluginInstall API handler. The force refresh functionality is now handled client-side through cache-busting headers and timestamp parameters added in previous commit (c7a9836).
- Add force parameter to plugin index fetch with cache-busting headers and timestamp
- Add openIndexView and reloadIndex methods to pluginInstallStore for explicit refresh
- Add request sequence tracking to prevent race conditions in concurrent index loads
- Move models summary state from component to store with loading/caching support
- Add refreshModelsSummary, ensureModelsSummaryLoaded, and modal