The message-feedback note editor previously expanded inline inside the
assistant message's shared IconActions row, overflowing the row at every
viewport and pushing the branch action and the clock out of the column.
Rework it into a portable popover: the note editor is a fixed-position panel
portaled to document.body and anchored to the note trigger, so the row keeps
its single 28px line whether the editor is open or not and the panel escapes
the column's overflow clip.
The like/dislike buttons and the note trigger stay in the row unchanged; the
trigger toggles the popover (textarea + Save/Cancel + note-save failure) which
auto-focuses the input and closes on Escape or an outside click, returning
focus to the trigger. Rating/list-load failures surface in the row, note-save
failures inside the popover. Reuse the Menu portal surface tokens and add
@types/react-dom so the createPortal usage typechecks.
Layout e2e sweeps six viewports and pins that opening the editor leaves the
row's overflow, line count, and out-of-column items unchanged, and that the
panel is outside the column, within the viewport, and anchored to its trigger.
Unit tests cover the popover's portal-to-body, toggle, Escape/outside-click
dismissal, and unmount early-returns.
Tianyi Cui