fix: improve canvas menu keyboard navigation and ARIA accessibility (#9526)

## Summary

The canvas mode selector popover (Select/Hand mode) uses plain `div`
elements for its menu items, making them completely inaccessible to
keyboard-only users and screen readers. This PR replaces them with
proper semantic HTML and ARIA attributes.

## Problem (AS-IS)

As reported in #9519, the canvas mode selector popover has the following
accessibility issues:

1. **Menu items are `div` elements** — they cannot receive keyboard
focus, so users cannot Tab into the popover or activate items with
Enter/Space. Keyboard-only users are completely locked out of switching
between Select and Hand (pan) mode via the popover.

2. **No ARIA roles** — screen readers announce the popover content as
generic text rather than an interactive menu. Users relying on assistive
technology have no way to understand that these are selectable options.

3. **No keyboard navigation within the popover** — even if a user
somehow focuses an item, there are no ArrowUp/ArrowDown handlers to move
between options, which is the standard interaction pattern for
`role="menu"` widgets (WAI-ARIA Menu Pattern).

4. **Decorative icons are not hidden from assistive technology** — icon
elements (`<i>` tags) are exposed to screen readers, adding noise to the
announcement.

5. **The bottom toolbar (`GraphCanvasMenu`) lacks semantic grouping** —
the `ButtonGroup` container has no `role="toolbar"` or `aria-label`, so
screen readers cannot convey that these buttons form a related control
group.

> Note: Pan mode itself already has keyboard shortcuts (`H` for
Hand/Lock, `V` for Select/Unlock), but the popover UI that surfaces
these options is not keyboard-accessible.

## Solution (TO-BE)

1. **Replace `div` → `button`** for menu items in `CanvasModeSelector` —
buttons are natively focusable and activatable via Enter/Space without
extra work.

2. **Add `role="menu"` on the container and `role="menuitem"` on each
option** — screen readers now announce "Canvas Mode menu" with two menu
items.

3. **Add ArrowUp/ArrowDown keyboard navigation** with wrap-around —
pressing ArrowDown on "Select" moves focus to "Hand", and vice versa.
This follows the WAI-ARIA Menu Pattern.

4. **Add `aria-label` to each menu item and `aria-hidden="true"` to
decorative icons** — screen readers announce "Select" / "Hand" clearly
without icon noise.

5. **Add `role="toolbar"` with `aria-label="Canvas Toolbar"` to the
`ButtonGroup`** — screen readers identify the bottom control bar as a
coherent toolbar.

## Changes

- **What**: Accessibility improvements to `CanvasModeSelector` popover
and `GraphCanvasMenu` toolbar
- **Dependencies**: None — only HTML/ARIA attribute changes and two new
i18n keys (`canvasMode`, `canvasToolbar`)

## Review Focus

- Verify the `button` elements render visually identical to the previous
`div` elements (same padding, hover styles, cursor)
- Confirm ArrowUp/ArrowDown navigation works correctly in the popover
- Check that screen readers announce the menu and toolbar correctly

Fixes #9519

> Note: The issue also requests Space-bar hold-to-pan, Tab through node
ports, and link creation mode keyboard shortcuts. These are significant
new features beyond the scope of this accessibility fix and should be
tracked separately.

## Test plan

- [x] Unit tests for ARIA roles, button elements, aria-labels,
aria-hidden, and arrow key navigation (7 tests)
- [ ] Manual: open canvas mode selector popover → Tab focuses first item
→ ArrowDown/ArrowUp navigates → Enter/Space selects
- [ ] Screen reader: verify "Canvas Mode menu" with "Select" and "Hand"
menu items are announced

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-9526-fix-improve-canvas-menu-keyboard-navigation-and-ARIA-accessibility-31c6d73d3650814c9487ecf748cf6a99)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

src/components/graph/CanvasModeSelector.vue

@@ -4,15 +4,21 @@
     variant="secondary"
     class="group h-8 rounded-none! bg-comfy-menu-bg p-0 transition-none! hover:rounded-lg! hover:bg-interface-button-hover-surface!"
     :style="buttonStyles"
+    :aria-label="$t('graphCanvasMenu.canvasMode')"
+    aria-haspopup="menu"
+    :aria-expanded="isOpen"
     @click="toggle"
   >
     <div class="flex items-center gap-1 pr-0.5">
       <div
         class="rounded-lg bg-interface-panel-selected-surface p-2 group-hover:bg-interface-button-hover-surface"
       >
-        <i :class="currentModeIcon" class="block size-4" />
+        <i :class="currentModeIcon" class="block size-4" aria-hidden="true" />
       </div>
-      <i class="icon-[lucide--chevron-down] block size-4 pr-1.5" />
+      <i
+        class="icon-[lucide--chevron-down] block size-4 pr-1.5"
+        aria-hidden="true"
+      />
     </div>
   </Button>
 
@@ -24,31 +30,54 @@
     :close-on-escape="true"
     unstyled
     :pt="popoverPt"
+    @show="onPopoverShow"
+    @hide="onPopoverHide"
   >
-    <div class="flex flex-col gap-1">
-      <div
-        class="flex cursor-pointer items-center justify-between px-3 py-2 text-sm hover:bg-node-component-surface-hovered"
+    <div
+      ref="menuRef"
+      class="flex flex-col gap-1"
+      role="menu"
+      :aria-label="$t('graphCanvasMenu.canvasMode')"
+    >
+      <button
+        type="button"
+        role="menuitemradio"
+        :aria-checked="!isCanvasReadOnly"
+        :tabindex="!isCanvasReadOnly ? 0 : -1"
+        class="flex w-full cursor-pointer items-center justify-between rounded-sm border-none bg-transparent px-3 py-2 text-sm text-text-primary outline-none hover:bg-node-component-surface-hovered focus-visible:bg-node-component-surface-hovered"
+        :aria-label="$t('graphCanvasMenu.select')"
         @click="setMode('select')"
+        @keydown.arrow-down.prevent="focusNextItem"
+        @keydown.arrow-up.prevent="focusPrevItem"
+        @keydown.escape.prevent="closeAndRestoreFocus"
       >
         <div class="flex items-center gap-2">
-          <i class="icon-[lucide--mouse-pointer-2] size-4" />
+          <i class="icon-[lucide--mouse-pointer-2] size-4" aria-hidden="true" />
           <span>{{ $t('graphCanvasMenu.select') }}</span>
         </div>
         <span class="text-[9px] text-text-primary">{{
           unlockCommandText
         }}</span>
-      </div>
+      </button>
 
-      <div
-        class="flex cursor-pointer items-center justify-between rounded-sm px-3 py-2 text-sm hover:bg-node-component-surface-hovered"
+      <button
+        type="button"
+        role="menuitemradio"
+        :aria-checked="isCanvasReadOnly"
+        :tabindex="isCanvasReadOnly ? 0 : -1"
+        class="flex w-full cursor-pointer items-center justify-between rounded-sm border-none bg-transparent px-3 py-2 text-sm text-text-primary outline-none hover:bg-node-component-surface-hovered focus-visible:bg-node-component-surface-hovered"
+        :aria-label="$t('graphCanvasMenu.hand')"
         @click="setMode('hand')"
+        @keydown.arrow-down.prevent="focusNextItem"
+        @keydown.arrow-up.prevent="focusPrevItem"
+        @keydown.escape.prevent="closeAndRestoreFocus"
       >
         <div class="flex items-center gap-2">
-          <i class="icon-[lucide--hand] size-4" />
+          <i class="icon-[lucide--hand] size-4" aria-hidden="true" />
           <span>{{ $t('graphCanvasMenu.hand') }}</span>
         </div>
         <span class="text-[9px] text-text-primary">{{ lockCommandText }}</span>
-      </div>
+      </button>
     </div>
   </Popover>
 </template>
@@ -56,7 +85,7 @@
 <script setup lang="ts">
 import Popover from 'primevue/popover'
 import type { ComponentPublicInstance } from 'vue'
-import { computed, ref } from 'vue'
+import { computed, nextTick, ref } from 'vue'
 
 import Button from '@/components/ui/button/Button.vue'
 import { useCanvasStore } from '@/renderer/core/canvas/canvasStore'
@@ -69,6 +98,8 @@ interface Props {
 defineProps<Props>()
 const buttonRef = ref<ComponentPublicInstance | null>(null)
 const popover = ref<InstanceType<typeof Popover>>()
+const menuRef = ref<HTMLElement | null>(null)
+const isOpen = ref(false)
 const commandStore = useCommandStore()
 const canvasStore = useCanvasStore()
 
@@ -106,6 +137,43 @@ const setMode = (mode: 'select' | 'hand') => {
   popover.value?.hide()
 }
 
+async function onPopoverShow() {
+  isOpen.value = true
+  await nextTick()
+  const checkedItem = menuRef.value?.querySelector<HTMLElement>(
+    '[aria-checked="true"]'
+  )
+  checkedItem?.focus()
+}
+
+function onPopoverHide() {
+  isOpen.value = false
+}
+
+function closeAndRestoreFocus() {
+  popover.value?.hide()
+  const el = buttonRef.value?.$el || buttonRef.value
+  ;(el as HTMLElement)?.focus()
+}
+
+function focusNextItem(event: KeyboardEvent) {
+  const items = getMenuItems(event)
+  const index = items.indexOf(event.target as HTMLElement)
+  items[(index + 1) % items.length]?.focus()
+}
+
+function focusPrevItem(event: KeyboardEvent) {
+  const items = getMenuItems(event)
+  const index = items.indexOf(event.target as HTMLElement)
+  items[(index - 1 + items.length) % items.length]?.focus()
+}
+
+function getMenuItems(event: KeyboardEvent): HTMLElement[] {
+  const menu = (event.target as HTMLElement).closest('[role="menu"]')
+  if (!menu) return []
+  return Array.from(menu.querySelectorAll('[role="menuitemradio"]'))
+}
+
 const popoverPt = computed(() => ({
   root: {
     class: 'absolute z-50 -translate-y-2'