fix: reset Custom Style draft on reopen

The modal is kept mounted by its parent (only `open` toggles), so Radix
onOpenChange never fires for a parent-driven open and the draft-reset
branch was dead code — abandoned edits leaked into the next open. Reset
on the `open` prop edge via effect instead. Also pass radix 10 to
parseInt for the size inputs. Adds a reopen-after-cancel regression test.

ha-relevant: yes

frontend/src/components/modals/__tests__/CustomStyleModal.test.tsx

@@ -134,4 +134,23 @@ describe('CustomStyleModal', () => {
     fireEvent.change(widthInputs[0], { target: { value: '250' } })
     expect((widthInputs[0] as HTMLInputElement).value).toBe('250')
   })
+
+  it('resets abandoned edits when reopened after cancel (mounted parent)', () => {
+    // Parent keeps the modal mounted and only toggles `open`, so the reset must
+    // happen on the open-prop edge, not via Radix onOpenChange.
+    const { rerender } = render(<CustomStyleModal open onClose={vi.fn()} />)
+    fireEvent.click(screen.getByRole('button', { name: 'Router' }))
+    const widthInput = screen.getAllByRole('spinbutton')[0]
+    fireEvent.change(widthInput, { target: { value: '250' } })
+    expect((widthInput as HTMLInputElement).value).toBe('250')
+
+    // Cancel = parent flips open → false, then later → true again.
+    rerender(<CustomStyleModal open={false} onClose={vi.fn()} />)
+    rerender(<CustomStyleModal open onClose={vi.fn()} />)
+
+    fireEvent.click(screen.getByRole('button', { name: 'Router' }))
+    const reopenedWidth = screen.getAllByRole('spinbutton')[0]
+    // Draft was reset to saved style (default width 0) — edit did not leak.
+    expect((reopenedWidth as HTMLInputElement).value).toBe('0')
+  })
 })