FIX: release the converter panel drag styles on unmount

frontend/src/components/Chat/ConverterPanel.test.tsx

@@ -134,6 +134,21 @@ function makePreviewResponse(
 }
 
 describe('ConverterPanel', () => {
+  it('releases the body cursor and selection lock when the panel unmounts mid drag', () => {
+    const panel = renderPanel()
+    fireEvent.mouseDown(screen.getByTestId('converter-panel-resize'))
+    expect(document.body.style.cursor).toBe('col-resize')
+    expect(document.body.style.userSelect).toBe('none')
+
+    // Unmount while the drag is still held: the mouseup listener is gone with
+    // the panel, so the cleanup is the only thing that can restore the body.
+    panel.rerender({ open: false })
+
+    expect(document.body.style.cursor).toBe('')
+    expect(document.body.style.userSelect).toBe('')
+  })
+
+
   beforeEach(() => {
     jest.clearAllMocks()
     mockedConvertersApi.listConverters.mockResolvedValue({ items: [textConverter] })

frontend/src/components/Chat/ConverterPanel/ConverterPanel.tsx

@@ -379,6 +379,14 @@ export default function ConverterPanel({
     return () => {
       document.removeEventListener('mousemove', handleMouseMove)
       document.removeEventListener('mouseup', handleMouseUp)
+      // Unmounting mid drag removes the mouseup listener before it can fire,
+      // so the body wide cursor and selection lock have to be released here or
+      // they stick until a full page reload.
+      if (isResizing.current) {
+        isResizing.current = false
+        document.body.style.cursor = ''
+        document.body.style.userSelect = ''
+      }
     }
   }, [])