fix(react-accordion): use inert='true' string attribute instead of boolean on closed panel

change/@fluentui-react-accordion-447fffcd-1e24-4145-babe-49abf6bc1134.json

@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: use empty string for inert attribute instead of boolean in AccordionPanel to prevent React DOM warning",
+  "packageName": "@fluentui/react-accordion",
+  "email": "198982749+Copilot@users.noreply.github.com",
+  "dependentChangeType": "patch"
+}

packages/react-components/react-accordion/library/src/components/AccordionPanel/AccordionPanel.test.tsx

@@ -38,7 +38,7 @@ describe('AccordionPanel', () => {
       <AccordionItemProvider value={mockAccordionItemContextValue({ open: false })}>{children}</AccordionItemProvider>
     );
     const { result } = renderHook(() => useAccordionPanelBase_unstable({}, ref), { wrapper });
-    expect(result.current.root.inert).toBe(true);
+    expect(result.current.root.inert).toBe('');
     expect(result.current.root.tabIndex).toBe(-1);
   });
 

packages/react-components/react-accordion/library/src/components/AccordionPanel/useAccordionPanel.ts

@@ -73,7 +73,7 @@ export const useAccordionPanelBase_unstable = (
         // Prevent keyboard focus from entering the panel while it is closed/collapsing.
         // tabIndex: -1 prevents the panel itself from being focused, and inert prevents
         // all focusable descendants from being reachable via keyboard navigation.
-        ...(open ? {} : { tabIndex: -1, inert: true }),
+        ...(open ? {} : { tabIndex: -1, inert: '' }),
       },
       { elementType: 'div' },
     ),