feat: nieuwe sprint wordt direct geselecteerd zonder redirect

createSprintAction zet nu de active-sprint cookie naar de zojuist
aangemaakte sprint, en de StartSprintButton refresht de huidige
pagina i.p.v. te redirecten naar /sprint. Resultaat: gebruiker blijft
op de product backlog en ziet de nieuwe sprint direct geselecteerd
in de sprint-pulldown.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

__tests__/actions/sprint-dates.test.ts

@@ -1,7 +1,7 @@
 import { describe, it, expect, vi, beforeEach } from 'vitest'
 
 vi.mock('next/cache', () => ({ revalidatePath: vi.fn() }))
-vi.mock('next/headers', () => ({ cookies: vi.fn().mockResolvedValue({}) }))
+vi.mock('next/headers', () => ({ cookies: vi.fn().mockResolvedValue({ set: vi.fn(), get: vi.fn(), delete: vi.fn() }) }))
 vi.mock('iron-session', () => ({
   getIronSession: vi.fn().mockResolvedValue({ userId: 'user-1', isDemo: false }),
 }))

actions/sprints.ts

@@ -72,6 +72,7 @@ export async function createSprintAction(_prevState: unknown, formData: FormData
       }),
   )
 
+  await setActiveSprintCookie(parsed.data.productId, sprint.id)
   revalidatePath(`/products/${parsed.data.productId}`)
   return { success: true, sprintId: sprint.id }
 }

components/sprint/start-sprint-button.tsx

@@ -51,7 +51,7 @@ export function StartSprintButton({ productId, isDemo = false }: StartSprintButt
       if (result?.success) {
         setOpen(false)
         setDirty(false)
-        router.push(`/products/${productId}/sprint`)
+        router.refresh()
       } else if (result?.code !== 422 && result?.error) {
         // Toast handled by caller; here we just keep the form open
       }