Messaging · Channels: the chat list, its rows, a channel's head and its pins

ChannelList sets chats down in sections, each a list: a press, an arrow
or Enter opens one, and the open chat is lit. A title names one section,
and a section holds a chat. ChannelItem shows a hash or a lock, its
unread count, a pin when pinned, and goes quiet when muted.
DirectMessageItem shows a person's initials with their presence. Unread
names stand out through ListItem's new strong; muted channels and
offline people go quiet through its quiet. ChannelHeader holds the name
and topic beside members, pins and a call, wrapping by the header rule.
PinnedMessages lists pins newest first; a press, an arrow or Enter opens
one, and Unpin lets one go. With none it shows a line and takes no Tab
stop.

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

TASKS.md

@@ -97,8 +97,12 @@ Per-component lines live in `tasks/`. Tags there:
 - [x] T27a Files · Items
 - [x] T27b Files · Explorer
 - [x] T27c Files · Find and look
-- [ ] T27d Files · Transfers
-- [ ] T28 Messaging
+- [x] T27d Files · Transfers
+- [ ] T28a Messaging · Channels
+- [ ] T28b Messaging · Messages
+- [ ] T28c Messaging · People
+- [ ] T28d Messaging · Calls
+- [ ] T28e Messaging · Stickers and GIFs
 - [ ] T29 Mail
 - [ ] T30 Calendar
 - [ ] T31 Project — `tasks/ch31-43.md`
@@ -328,3 +332,4 @@ Per-component lines live in `tasks/`. Tags there:
 | T27c | 1 | FAIL | recent and found files were keyed by their place, so the cursor left a file an open moved |
 | T27c | 2 | PASS | |
 | T27d | 1 | FAIL | a press on a finished download's Show button also opened the file through its row |
+| T27d | 2 | PASS | |