refactor(web): migrate priority change to oRPC contract with useMutation

- Add changePreferredProviderType contract in model-providers.ts
- Register in consoleRouterContract
- Replace raw async changeModelProviderPriority with useMutation
- Use Toast.notify (static API) instead of useToastContext hook
- Pass isPending as isChangingPriority to disable buttons during switch
- Add disabled prop to UsagePrioritySection
- Fix pre-existing test assertions for api-unavailable variant
- Update all specs with isChangingPriority prop and oRPC mock pattern

web/contract/console/model-providers.ts

@@ -1,4 +1,5 @@
-import type { ModelItem } from '@/app/components/header/account-setting/model-provider-page/declarations'
+import type { ModelItem, PreferredProviderTypeEnum } from '@/app/components/header/account-setting/model-provider-page/declarations'
+import type { CommonResponse } from '@/models/common'
 import { type } from '@orpc/contract'
 import { base } from '../base'
 
@@ -15,3 +16,18 @@ export const modelProvidersModelsContract = base
   .output(type<{
     data: ModelItem[]
   }>())
+
+export const changePreferredProviderTypeContract = base
+  .route({
+    path: '/workspaces/current/model-providers/{provider}/preferred-provider-type',
+    method: 'POST',
+  })
+  .input(type<{
+    params: {
+      provider: string
+    }
+    body: {
+      preferred_provider_type: PreferredProviderTypeEnum
+    }
+  }>())
+  .output(type<CommonResponse>())