Seed sidebar default pages lazily on expansion, scope page-tab dedupe
to the target pane, let a sole tab split its own pane with a factory
backfill, close menus when focus enters a sandboxed iframe, and pin the
code preview copy banner while unifying its background with the pane.
- Split toggle aria-labels from their tooltips: the sidebar expand/collapse
buttons announce "Open/Collapse right sidebar" so the two sidebars stay
distinguishable, and the wrap toggle keeps an invariant "Line wrap" name
beside aria-pressed while the tooltip keeps the action wording.
- A hidden tab close also takes no pointer events, so a touch press on the
chip's trailing edge activates the tab instead of closing it; e2e closes
hover the chip first, the way a reader would.
- Closing the last docked tab in fullscreen hands the mode back to push, so
the next expand does not give the whole window to the start page.
- The drop scrim mixes from bg-base, not bg-layer-2, which dark mode binds
to a lighter bluish step than the column beneath it.
- Document the menuitem probe in TabMenuExtras and the strip fade's known
gap; match the open-in-app split-button comment to the 28px control row.
Chip capsules with scroll fades and live titles, drop-zone hint cards, the
canCloseTab control policy with the quiet lone chip and self-dismissing empty
menu, and a room reading that stays independent of hidden split controls.
Yif