message: feat: Add panel-header token for FixedLayout/ModalRoot/Panel/SplitLayout + fix layout for PanelHeader
diff: position: relative;
  z-index: 11;
  margin-top: calc(
  - -1 * (var(--panelheader_height) + var(--safe-area-inset-top))
  + -1 * (var(
  + --panelheader_height,
  + var(--vkui--size_panel_header_height--regular)
  + ) + var(--safe-area-inset-top))
  );
  }
  .SplitLayout--ios .SplitLayout__inner--header {
  margin-top: calc(
  - -1 * (var(--panelheader_height_ios) + var(--safe-area-inset-top))
  + -1 * (var(
  + --panelheader_height_ios,
  + var(--vkui--size_panel_header_height--regular)
  + ) + var(--safe-area-inset-top))
  );
  }
  