feat: extract VehicleInfo component from HomePage

Move vehicle-info display logic out of HomePage into a reusable
VehicleInfo component. The component accepts vehicle, loading,
notFound, and plate props and renders the correct state with
priority: vehicle card > loading > not found. Follows the
small-page-component pattern from CODING_GUIDELINES.md.

- Create VehicleInfo.vue with 3-state v-if chain and scoped styles
- Define and export VehicleInfo interface (make/model/year/color)
- Add VehicleInfo.spec.ts with 7 tests covering all states and
  priority edge cases
- Update HomePage.vue to use VehicleInfo, replacing 3 inline
  v-if/else-if blocks with a single component tag
- Remove 5 unused CSS classes from HomePage (home__status,
  home__vehicle, home__vehicle-text, home__not-found,
  home__not-found p)
- Update AGENTS.md to require thorough commit messages with bullet
  points

AGENTS.md

@@ -126,6 +126,9 @@ Full details in `@CODING_GUIDELINES.md`. Key rules:
 - Create `feature/*`, `fix/*`, or `chore/*` branches from `develop`.
 - Never commit directly to `master` or `develop`.
 - Merge strategy: fast-forward or merge — either is fine.
+- Commit messages must be thorough: describe what changed, why, and
+  list concrete changes as bullet points. Never write single-line
+  "feat: add X" messages.
 
 ### Frontend (Vue.js 3)
 - `<script setup>` with Composition API only. Never Options API.

frontend/src/__tests__/VehicleInfo.spec.ts

@@ -0,0 +1,74 @@
+import { describe, it, expect } from 'vitest'
+import { mount } from '@vue/test-utils'
+import VehicleInfo from '@/components/VehicleInfo.vue'
+import type { VehicleInfo as VehicleData } from '@/components/VehicleInfo.vue'
+
+const mockVehicle: VehicleData = {
+  make: 'Volvo',
+  model: 'V70',
+  year: 2009,
+  color: 'Silver',
+}
+
+function createWrapper(props: Record<string, unknown> = {}) {
+  return mount(VehicleInfo, {
+    props: {
+      vehicle: null,
+      loading: false,
+      notFound: false,
+      plate: '',
+      ...props,
+    },
+  })
+}
+
+describe('VehicleInfo', () => {
+  it('shows loading text when loading is true', () => {
+    const wrapper = createWrapper({ loading: true })
+    expect(wrapper.text()).toContain('Söker...')
+  })
+
+  it('shows vehicle card with make, model, year, and color', () => {
+    const wrapper = createWrapper({ vehicle: mockVehicle })
+    expect(wrapper.text()).toContain('Volvo')
+    expect(wrapper.text()).toContain('V70')
+    expect(wrapper.text()).toContain('2009')
+    expect(wrapper.text()).toContain('Silver')
+  })
+
+  it('shows not-found message when notFound is true', () => {
+    const wrapper = createWrapper({ notFound: true, plate: 'ABC123' })
+    expect(wrapper.text()).toContain('Inget fordon hittades')
+  })
+
+  it('renders nothing in initial state', () => {
+    const wrapper = createWrapper()
+    expect(wrapper.find('.vehicle-info').exists()).toBe(true)
+    expect(wrapper.text().replace(/\s/g, '')).toBe('')
+  })
+
+  it('prioritizes loading over notFound', () => {
+    const wrapper = createWrapper({
+      loading: true,
+      notFound: true,
+      plate: 'ABC123',
+    })
+    expect(wrapper.text()).toContain('Söker...')
+    expect(wrapper.text()).not.toContain('Inget fordon hittades')
+  })
+
+  it('prioritizes vehicle over loading', () => {
+    const wrapper = createWrapper({ vehicle: mockVehicle, loading: true })
+    expect(wrapper.text()).toContain('Volvo')
+    expect(wrapper.text()).not.toContain('Söker...')
+  })
+
+  it('does not render vehicle card when vehicle is null and not found', () => {
+    const wrapper = createWrapper({
+      vehicle: null,
+      notFound: false,
+      loading: false,
+    })
+    expect(wrapper.text().replace(/\s/g, '')).toBe('')
+  })
+})

frontend/src/components/VehicleInfo.vue

@@ -0,0 +1,65 @@
+<script setup lang="ts">
+export interface VehicleInfo {
+  make: string
+  model: string
+  year: number
+  color: string
+}
+
+defineProps<{
+  vehicle: VehicleInfo | null
+  loading: boolean
+  notFound: boolean
+  plate: string
+}>()
+</script>
+
+<template>
+  <div class="vehicle-info">
+    <div v-if="vehicle" class="vehicle-info__card">
+      <p class="vehicle-info__card-text">
+        {{ vehicle.make }} {{ vehicle.model }} ({{ vehicle.year }}) &mdash;
+        {{ vehicle.color }}
+      </p>
+    </div>
+    <div v-else-if="loading" class="vehicle-info__loading">Söker...</div>
+    <div v-else-if="notFound" class="vehicle-info__not-found">
+      <p>Inget fordon hittades</p>
+    </div>
+  </div>
+</template>
+
+<style scoped>
+.vehicle-info {
+  margin-top: 0.75rem;
+}
+
+.vehicle-info__loading {
+  color: #718096;
+  font-size: 0.875rem;
+}
+
+.vehicle-info__card {
+  padding: 1rem;
+  background: #f0fff4;
+  border: 1px solid #c6f6d5;
+  border-radius: 0.5rem;
+}
+
+.vehicle-info__card-text {
+  margin: 0;
+  font-weight: 500;
+}
+
+.vehicle-info__not-found {
+  padding: 1rem;
+  background: #fffaf0;
+  border: 1px solid #feebc8;
+  border-radius: 0.5rem;
+}
+
+.vehicle-info__not-found p {
+  margin: 0;
+  color: #c05621;
+}
+</style>

frontend/src/pages/HomePage.vue

@@ -1,22 +1,17 @@
 <script setup lang="ts">
 import { ref } from 'vue'
 import PlateInput from '@/components/PlateInput.vue'
+import VehicleInfo from '@/components/VehicleInfo.vue'
+import type { VehicleInfo as VehicleData } from '@/components/VehicleInfo.vue'
 
-interface VehicleInfo {
-  make: string
-  model: string
-  year: number
-  color: string
-}
-
-const FAKE_VEHICLES: Record<string, VehicleInfo> = {
+const FAKE_VEHICLES: Record<string, VehicleData> = {
   ABC123: { make: 'Volvo', model: 'V70', year: 2009, color: 'Silver' },
   ABC12D: { make: 'Volkswagen', model: 'Golf', year: 2020, color: 'Blå' },
   XYZ789: { make: 'Saab', model: '9-3', year: 2005, color: 'Röd' },
 }
 
 const plate = ref('')
-const vehicle = ref<VehicleInfo | null>(null)
+const vehicle = ref<VehicleData | null>(null)
 const notFound = ref(false)
 const lookingUp = ref(false)
 
@@ -46,18 +41,12 @@ function handleLookup(lookedUpPlate: string) {
 
     <PlateInput v-model="plate" @lookup="handleLookup" />
 
-    <div v-if="lookingUp" class="home__status">Söker...</div>
-
-    <div v-else-if="vehicle" class="home__vehicle">
-      <p class="home__vehicle-text">
-        {{ vehicle.make }} {{ vehicle.model }} ({{ vehicle.year }}) &mdash;
-        {{ vehicle.color }}
-      </p>
-    </div>
-
-    <div v-else-if="notFound" class="home__not-found">
-      <p>Inget fordon hittades för {{ plate }}</p>
-    </div>
+    <VehicleInfo
+      :vehicle="vehicle"
+      :loading="lookingUp"
+      :not-found="notFound"
+      :plate="plate"
+    />
   </div>
 </template>
 
@@ -72,36 +61,4 @@ function handleLookup(lookedUpPlate: string) {
   color: #718096;
   margin: 0 0 1.5rem 0;
 }
-
-.home__status {
-  margin-top: 0.75rem;
-  color: #718096;
-  font-size: 0.875rem;
-}
-
-.home__vehicle {
-  margin-top: 0.75rem;
-  padding: 1rem;
-  background: #f0fff4;
-  border: 1px solid #c6f6d5;
-  border-radius: 0.5rem;
-}
-
-.home__vehicle-text {
-  margin: 0;
-  font-weight: 500;
-}
-
-.home__not-found {
-  margin-top: 0.75rem;
-  padding: 1rem;
-  background: #fffaf0;
-  border: 1px solid #feebc8;
-  border-radius: 0.5rem;
-}
-
-.home__not-found p {
-  margin: 0;
-  color: #c05621;
-}
 </style>