Mail · a folded message keeps focus as it opens, and gives way at 280px

Each message in a thread holds one focus handle, a Tab stop while
folded and tracked on the letter once open, so a keyboard open keeps
focus on the message and Tab goes on to its Reply. A press on a fold
leaves focus alone. A fold's name now gives way with its words, so a
long name beside a long date stays inside the row.

AGENTS.md

@@ -74,7 +74,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - gpui runs the click of every pressed element under the pointer, a row's with its button's. A pressable row that holds buttons stops their press at their box on mouse down (`files::transfer`), as `overlays::media_button` stops its own.
 - gpui draws a window's first frame inside `open_window`. State the first frame reads, such as `cx.set_menus`, is set before it opens.
 - gpui clicks a focused element when Enter or Space is released. An overlay that hands focus back picks on release too; a pick on press returns focus first, and the release clicks the opener again. An edit in place that hands focus back keeps its text on Enter's release (`forms::InlineEdit`). The press itself bubbles, so a container that takes Space leaves a focused button its own: `overlays::media_button` stops it, and a button in a `SelectableList` row stops Space and Enter at its box (`mail::MailItem`'s star, `messaging::PinnedMessages`' Unpin).
-- A focus handle a component hands back lives across all its modes: take it with `tab_stop` before any early return, or keyed state drops it while the other mode draws and the handed-back focus lands nowhere.
+- A focus handle a component hands back lives across all its modes: take it with `tab_stop` before any early return, or keyed state drops it while the other mode draws and the handed-back focus lands nowhere. A thread's message keeps one handle folded and open, a Tab stop only while folded (`mail::MailThreadView`).
 - A dialog goes through `overlays::Dialog`: scrim, focus trap, Escape and focus return live there. Its close runs on every way out, so a dialog with two answers marks the chosen one before it closes (`messaging::IncomingCallDialog`). AlertDialog, ConfirmDialog and PromptDialog build on it; a fullscreen dialog fills the window below its title bar. A dialog's card fits the window, a title bar's height clear at each end; its body scrolls and its actions stay.
 - Controls on a dark layer over pictures are `overlays::media_button`, light icons that dim when they have nowhere to go, for the lightbox and a video player's bar alike.
 - A component's letter keys step aside while Command or Control is held, so the app's shortcuts reach the app (`media::ImageAnnotator`, `VideoPlayer`, `VideoThumbnailStrip`).