Mail · Boxes and lists: mailboxes, folders and labels, the mail list, inbox zero

MailboxList sets mailboxes, folders and labels in sections: a press, an
arrow or Enter opens one, the open one lit; a box with mail unread
stands out with its count, and a label wears one of the theme's chart
hues. MailList holds messages in a multiple-select list: the sender
strong beside a dot while unread, the subject and first words under
it, the time today, the weekday this week, the date this year or with
its year, a paperclip for files, and a star whose press stays off the
row. InboxZeroState points to feedback::EmptyState.

Sections of selectable lists now have one home, lists::Sections, which
ChannelList and MemberList use too; ListItem gains a third line.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

AGENTS.md

@@ -134,7 +134,7 @@ Ely GPUI Component. A component library for GPUI, in light and dark.
 - A mode that leaves on Escape holds its own focus through `primitives::hold_focus`: turned on while focus is elsewhere, it takes focus so Escape reaches it, and `hand_back` returns it (`documents::ZenMode`, `collab::FollowMode`).
 - A chat holds at its newest message through gpui's `list` with `ListAlignment::Bottom`: it sticks while scrolled to the end, and `scroll_to` one past the last item sticks it again; that call sends no scroll event, so the owner clears its own away state (`chat::MessageList`).
 - Anything pressable is a Tab stop: a row, card or toggle takes `tab_index(0)` and `focus_ring`, with a 1px border that stays transparent where it shows none; gpui presses it on the release of Enter or Space.
-- A list of pressable rows goes through `lists::SelectableList`, whose cursor reaches them by key: Up and Down move, Enter or a double press activates (`media::Playlist`). A bare `ListItem` press is the pointer's only.
+- A list of pressable rows goes through `lists::SelectableList`, whose cursor reaches them by key: Up and Down move, Enter or a double press activates (`media::Playlist`). A bare `ListItem` press is the pointer's only. Titled sections of such lists go through `lists::Sections`, for ChannelList, MemberList and MailboxList; each owner builds its rows and keeps its own checks.
 - A row that holds text beside fixed parts lets the text give way: the text takes `flex_1().min_w_0()` and an `Ellipsis`; counts, icons, dates and chevrons take `flex_none`. A label that must stay whole wraps in that block instead, as `forms::Checkbox`'s does.
 - A mark over a text field reads the field at paint time, from a canvas laid over it (`collab::RemoteCursor`): by then `TextInput::bounds_for` holds this frame's layout, and a still page never renders again to catch up.
 - A callback field holds a named `type` alias; clippy's type_complexity rejects `Option<Rc<dyn Fn(..)>>`. A chapter shares one alias per shape.