fix(hermes): show active provider and wire add/enable/remove actions

Switching a Hermes provider previously only fired a toast because the frontend treated Hermes as non-additive (unlike backend AppType::is_additive_mode, which lists OpenCode | OpenClaw | Hermes) and relied on the unused is_current DB flag for highlighting. Align the UI model with the backend:

- Include Hermes in ProviderActions' isAdditiveMode so the main button switches between "Add" and "Remove".
- Drive the "current" highlight from model.provider (via useHermesModelConfig) instead of the DB is_current field; model.provider is Hermes's real SSOT for the active provider.
- Reuse OpenClaw's set-as-default button slot to expose an "Enable" action on Hermes that calls switchProvider, so providers already in config can be activated without re-adding. switch_normal + apply_switch_defaults already atomically update custom_providers and model.provider, so no backend change is needed.
- Invalidate liveProviderIds + modelConfig + health in parallel after add/update/delete/switch via a new invalidateHermesProviderCaches helper, replacing four copies of three sequential awaits.

src/hooks/useHermes.ts

@@ -1,4 +1,9 @@
-import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
+import {
+  useMutation,
+  useQuery,
+  useQueryClient,
+  type QueryClient,
+} from "@tanstack/react-query";
 import { hermesApi } from "@/lib/api/hermes";
 import { providersApi } from "@/lib/api/providers";
 import type {
@@ -20,6 +25,19 @@ export const hermesKeys = {
   health: ["hermes", "health"] as const,
 };
 
+/**
+ * Invalidate all Hermes caches that may change when a provider is
+ * added/updated/deleted/switched. Runs invalidations in parallel so the
+ * caller doesn't await three sequential refetches.
+ */
+export function invalidateHermesProviderCaches(queryClient: QueryClient) {
+  return Promise.all([
+    queryClient.invalidateQueries({ queryKey: hermesKeys.liveProviderIds }),
+    queryClient.invalidateQueries({ queryKey: hermesKeys.modelConfig }),
+    queryClient.invalidateQueries({ queryKey: hermesKeys.health }),
+  ]);
+}
+
 // ============================================================
 // Query hooks
 // ============================================================