feat(timeline): reverse-chronologische volgorde + unit-test merge/sort

Extraheert mergeTimelineItems uit IdeaTimeline als exporteerbare functie
en voegt een vitest-test toe die de nieuwste-boven-sortering verifieert.
revalidatePath in user-questions action was al aanwezig.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

__tests__/components/idea-timeline-merge.test.ts

@@ -0,0 +1,44 @@
+import { describe, it, expect } from 'vitest'
+import { mergeTimelineItems } from '@/components/ideas/idea-timeline'
+
+describe('mergeTimelineItems', () => {
+  it('sorteert reverse-chronologisch: nieuwste entry staat eerst', () => {
+    const logs = [
+      { id: 'l1', type: 'NOTE', content: 'oud', metadata: null, created_at: '2024-01-01T10:00:00.000Z' },
+    ]
+    const questions = [
+      {
+        id: 'q1',
+        question: 'Vraag?',
+        options: null,
+        status: 'open' as const,
+        answer: null,
+        created_at: '2024-01-03T12:00:00.000Z',
+        expires_at: '2024-01-10T12:00:00.000Z',
+      },
+    ]
+    const userQuestions = [
+      {
+        id: 'uq1',
+        question: 'Mijn vraag',
+        answer: null,
+        status: 'pending' as const,
+        created_at: '2024-01-02T08:00:00.000Z',
+      },
+    ]
+
+    const result = mergeTimelineItems(logs, questions, userQuestions)
+
+    expect(result).toHaveLength(3)
+    expect(result[0].created_at).toBe('2024-01-03T12:00:00.000Z')
+    expect(result[0].kind).toBe('question')
+    expect(result[1].created_at).toBe('2024-01-02T08:00:00.000Z')
+    expect(result[1].kind).toBe('user_question')
+    expect(result[2].created_at).toBe('2024-01-01T10:00:00.000Z')
+    expect(result[2].kind).toBe('log')
+  })
+
+  it('geeft lege lijst terug bij geen input', () => {
+    expect(mergeTimelineItems([], [], [])).toEqual([])
+  })
+})

components/ideas/idea-timeline.tsx

@@ -99,6 +99,23 @@ const USER_QUESTION_STATUS_LABEL: Record<TimelineUserQuestion['status'], string>
   answered: 'Beantwoord',
 }
 
+export type TimelineEntry =
+  | { kind: 'log'; created_at: string; data: TimelineLog }
+  | { kind: 'question'; created_at: string; data: TimelineQuestion }
+  | { kind: 'user_question'; created_at: string; data: TimelineUserQuestion }
+
+export function mergeTimelineItems(
+  logs: TimelineLog[],
+  questions: TimelineQuestion[],
+  userQuestions: TimelineUserQuestion[],
+): TimelineEntry[] {
+  return [
+    ...logs.map((l) => ({ kind: 'log' as const, created_at: l.created_at, data: l })),
+    ...questions.map((q) => ({ kind: 'question' as const, created_at: q.created_at, data: q })),
+    ...userQuestions.map((uq) => ({ kind: 'user_question' as const, created_at: uq.created_at, data: uq })),
+  ].sort((a, b) => (a.created_at < b.created_at ? 1 : -1))
+}
+
 export function IdeaTimeline({
   logs,
   questions,
@@ -107,23 +124,7 @@ export function IdeaTimeline({
   ideaId,
   isDemo = false,
 }: Props) {
-  const merged = [
-    ...logs.map((l) => ({
-      kind: 'log' as const,
-      created_at: l.created_at,
-      data: l,
-    })),
-    ...questions.map((q) => ({
-      kind: 'question' as const,
-      created_at: q.created_at,
-      data: q,
-    })),
-    ...userQuestions.map((uq) => ({
-      kind: 'user_question' as const,
-      created_at: uq.created_at,
-      data: uq,
-    })),
-  ].sort((a, b) => (a.created_at < b.created_at ? 1 : -1))
+  const merged = mergeTimelineItems(logs, questions, userQuestions)
 
   const showChatInput = planMd !== null