fix(ui-modal): add whitespace between header text nodes in scroll body aria-label

The Modal body's scroll aria-label is assembled from the header's text nodes,
which were concatenated with no separator. When the header contains a Heading
with `aiVariant` (which renders a decorative "IgniteAI" text node before the
title), this produced malformed labels like "IgniteAIAI Nutrition Facts" that
VoiceOver announced incorrectly (WCAG 1.3.1).

Trim each text node and join non-empty ones with a single space so adjacent
text nodes from different elements are separated. Applies to the v2 ModalHeader.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: git-nandor

packages/ui-modal/src/Modal/__tests__/ModalBody.test.tsx

@@ -31,7 +31,7 @@ import canvas from '@instructure/ui-themes'
 import { View } from '@instructure/ui-view/latest'
 import type { ViewOwnProps } from '@instructure/ui-view/latest'
 
-import { ModalBody } from '@instructure/ui-modal/latest'
+import { Modal, ModalBody, ModalHeader } from '@instructure/ui-modal/latest'
 
 const BODY_TEXT = 'Modal-body-text'
 
@@ -209,5 +209,36 @@ describe('<ModalBody />', () => {
 
       await waitFor(() => expect(body).not.toHaveAttribute('tabindex'))
     })
+
+    it('labels the scrollable body from the header with a space between adjacent text nodes', async () => {
+      mockScrollable(true)
+      // The header reproduces what a `Heading` with `aiVariant="stacked"`
+      // renders: a decorative "IgniteAI" text node immediately followed by the
+      // title, with no whitespace between them. The body's aria-label must not
+      // collapse these into "IgniteAI Nutrition Facts".
+      const { findByText } = render(
+        <Modal
+          open
+          label="AI information"
+          size="small"
+          shouldReturnFocus={false}
+          onDismiss={() => {}}
+        >
+          <ModalHeader>
+            <span aria-hidden="true">IgniteAI</span>
+            {'AI Nutrition Facts'}
+          </ModalHeader>
+          <ModalBody>{BODY_TEXT}</ModalBody>
+        </Modal>
+      )
+      const body = await findByText(BODY_TEXT)
+
+      await waitFor(() =>
+        expect(body).toHaveAttribute(
+          'aria-label',
+          'IgniteAI AI Nutrition Facts'
+        )
+      )
+    })
   })
 })

packages/ui-modal/src/Modal/v2/ModalHeader/index.tsx

@@ -75,12 +75,19 @@ class ModalHeader extends Component<ModalHeaderProps> {
           : NodeFilter.FILTER_ACCEPT
       }
     })
-    let text = ''
+    const textParts: string[] = []
     let current
     while ((current = walker.nextNode())) {
-      text += current.nodeValue
+      // Trim each text node and drop empty ones so adjacent text nodes from
+      // different elements (e.g. the decorative "IgniteAI" span a `Heading`
+      // with `aiVariant` renders before its title) are separated by a single
+      // space instead of being concatenated into "IgniteAI Nutrition Facts".
+      const value = current.nodeValue?.trim()
+      if (value) {
+        textParts.push(value)
+      }
     }
-    return text
+    return textParts.join(' ')
   }
 
   handleRef = (el: HTMLDivElement | null) => {