fix: add arrow-key roving tabindex nav and aria-pressed to triage views

KanbanBoard's board tabs implemented roving tabindex but never wired up
arrow-key navigation, making inactive tabs keyboard-unreachable. Adds
ArrowLeft/ArrowRight/Home/End handling that moves both selection and
focus between tabs, closing an unmet requirement from the original
design doc. Also adds aria-pressed to App's List/Board toggle buttons
so their active state is exposed to assistive technology, not just
conveyed visually via CSS class.

frontend/src/App.vue

@@ -67,6 +67,7 @@ onMounted(async () => {
       <div class="view-toggle">
         <button
           type="button"
+          :aria-pressed="viewMode === 'list'"
           :class="{ active: viewMode === 'list' }"
           @click="viewMode = 'list'"
         >
@@ -74,6 +75,7 @@ onMounted(async () => {
         </button>
         <button
           type="button"
+          :aria-pressed="viewMode === 'board'"
           :class="{ active: viewMode === 'board' }"
           @click="viewMode = 'board'"
         >

frontend/src/components/KanbanBoard.vue

@@ -1,5 +1,5 @@
 <script setup>
-import { ref, computed, watch } from 'vue'
+import { ref, computed, watch, nextTick } from 'vue'
 import ModalityBadge from './ModalityBadge.vue'
 import { DONATION_STAGES, OTHER_STAGES, OUTBOUND_STAGES, UNSORTED_STAGES, STAGE_LABELS } from '../stages.js'
 
@@ -50,6 +50,31 @@ function selectBoard(key) {
   activeBoardKey.value = key
 }
 
+const tabRefs = ref([])
+
+function setTabRef(el, index) {
+  tabRefs.value[index] = el
+}
+
+async function handleTabKeydown(event, index) {
+  let nextIndex = null
+  if (event.key === 'ArrowRight') {
+    nextIndex = (index + 1) % BOARDS.length
+  } else if (event.key === 'ArrowLeft') {
+    nextIndex = (index - 1 + BOARDS.length) % BOARDS.length
+  } else if (event.key === 'Home') {
+    nextIndex = 0
+  } else if (event.key === 'End') {
+    nextIndex = BOARDS.length - 1
+  } else {
+    return
+  }
+  event.preventDefault()
+  selectBoard(BOARDS[nextIndex].key)
+  await nextTick()
+  tabRefs.value[nextIndex]?.focus()
+}
+
 function selectStage(stage) {
   activeStage.value = stage
 }
@@ -63,8 +88,9 @@ function labelFor(stage) {
   <div class="kanban-board">
     <div class="board-tabs" role="tablist" aria-label="Item category">
       <button
-        v-for="board in BOARDS"
+        v-for="(board, index) in BOARDS"
         :key="board.key"
+        :ref="el => setTabRef(el, index)"
         role="tab"
         :id="`board-tab-${board.key}`"
         :aria-selected="board.key === activeBoardKey"
@@ -74,6 +100,7 @@ function labelFor(stage) {
         class="board-tab"
         :class="{ active: board.key === activeBoardKey }"
         @click="selectBoard(board.key)"
+        @keydown="handleTabKeydown($event, index)"
       >
         {{ board.label }} ({{ boardCount(board.key) }})
       </button>

frontend/tests/App.spec.js

@@ -42,4 +42,13 @@ describe('App view mode', () => {
     await boardButton.trigger('click')
     expect(localStorage.getItem('chorus_view_mode')).toBe('board')
   })
+
+  it('sets aria-pressed correctly on the view toggle buttons', async () => {
+    const wrapper = mount(App)
+    await flushPromises()
+    const listButton = wrapper.findAll('.view-toggle button').find((b) => b.text() === 'List')
+    const boardButton = wrapper.findAll('.view-toggle button').find((b) => b.text() === 'Board')
+    expect(listButton.attributes('aria-pressed')).toBe('true')
+    expect(boardButton.attributes('aria-pressed')).toBe('false')
+  })
 })

frontend/tests/KanbanBoard.spec.js

@@ -84,4 +84,24 @@ describe('KanbanBoard', () => {
     expect(activeColumns).toHaveLength(1)
     expect(activeColumns[0].text()).toContain('New')
   })
+
+  it('ArrowRight on a board tab moves selection and focus to the next tab', async () => {
+    const wrapper = mount(KanbanBoard, { props: { items: [] }, attachTo: document.body })
+    const tabs = wrapper.findAll('[role="tab"]')
+    tabs[0].element.focus()
+    await tabs[0].trigger('keydown', { key: 'ArrowRight' })
+    const updatedTabs = wrapper.findAll('[role="tab"]')
+    expect(updatedTabs[1].attributes('aria-selected')).toBe('true')
+    expect(document.activeElement).toBe(updatedTabs[1].element)
+    wrapper.unmount()
+  })
+
+  it('ArrowLeft wraps from the first tab to the last tab', async () => {
+    const wrapper = mount(KanbanBoard, { props: { items: [] }, attachTo: document.body })
+    const tabs = wrapper.findAll('[role="tab"]')
+    await tabs[0].trigger('keydown', { key: 'ArrowLeft' })
+    const updatedTabs = wrapper.findAll('[role="tab"]')
+    expect(updatedTabs[3].attributes('aria-selected')).toBe('true')
+    wrapper.unmount()
+  })
 })