fix(desktop): gate prompts on provider setup

Show the desktop provider onboarding flow before prompt submission when no inference provider is configured, preventing fresh installs from falling through to backend credential errors.

apps/desktop/src/app/session/hooks/use-prompt-actions.ts

@@ -25,6 +25,7 @@ import {
   type ComposerAttachment
 } from '@/store/composer'
 import { clearNotifications, notify, notifyError } from '@/store/notifications'
+import { requestDesktopOnboarding } from '@/store/onboarding'
 import { $busy, $messages, setAwaitingResponse, setBusy, setMessages } from '@/store/session'
 
 import type { ClientSessionState, ImageAttachResponse, SlashExecResponse } from '../../types'
@@ -45,6 +46,16 @@ function blobToDataUrl(blob: Blob): Promise<string> {
   })
 }
 
+interface SetupStatus {
+  provider_configured?: boolean
+}
+
+function isProviderSetupError(error: unknown) {
+  const message = error instanceof Error ? error.message : String(error)
+
+  return /No inference provider configured|OPENROUTER_API_KEY|OPENAI_API_KEY|ANTHROPIC_API_KEY/i.test(message)
+}
+
 interface PromptActionsOptions {
   activeSessionId: string | null
   activeSessionIdRef: MutableRefObject<string | null>
@@ -216,6 +227,15 @@ export function usePromptActions({
       setAwaitingResponse(true)
       clearNotifications()
 
+      const setup = await requestGateway<SetupStatus>('setup.status').catch(() => null)
+
+      if (setup?.provider_configured === false) {
+        releaseBusy()
+        requestDesktopOnboarding('Add a provider credential before sending your first message.')
+
+        return
+      }
+
       let sessionId = activeSessionId
 
       if (!sessionId) {
@@ -257,6 +277,13 @@ export function usePromptActions({
       } catch (err) {
         releaseBusy()
         updateSessionState(sessionId, state => ({ ...state, busy: false, awaitingResponse: false }))
+
+        if (isProviderSetupError(err)) {
+          requestDesktopOnboarding('Add a provider credential before sending your first message.')
+
+          return
+        }
+
         notifyError(err, 'Prompt failed')
       }
     },