Add chat components 321-345; named List rows, inert scroll views

Speech bubbles, a chat log that follows its end, a composer that sends
on Enter, typing dots, chat and channel lists, read receipts,
reactions, emoji and sticker pickers, mentions, date and unread rules,
system lines, member lists, user cards, a mailbox, mail reader and
letter, a notification bell, call controls, a voice meter, attachment
chips, link previews and polls.

pixel's editor takes EnterSends; display's Bubble takes a Fill and
exports EmojiSprite. data.List names its rows, which also lets typing
choose one. layout.ScrollArea and input.TextArea hold still under
Inert, and an inert scroll view leaves the Tab order until it wakes.

pixel/editor.go

@@ -17,6 +17,8 @@ type EditorOptions struct {
 	Placeholder string
 	Label       string
 	Disabled    bool
+	// EnterSends submits a multi-line field on Enter; Shift+Enter breaks lines.
+	EnterSends bool
 }
 
 type Edit struct {
@@ -33,6 +35,7 @@ type editLine struct{ start, end int }
 
 type editEnv struct {
 	multi  bool
+	sends  bool
 	maxLen int
 	mask   rune
 	width  int
@@ -47,6 +50,9 @@ func Editor(c *ui.Context, value *string, o EditorOptions) Edit {
 	if o.MaxLength < 0 {
 		panic(fmt.Sprintf("pixel: MaxLength %d", o.MaxLength))
 	}
+	if o.EnterSends && !o.Multiline {
+		panic("pixel: EnterSends needs a multi-line field")
+	}
 	shell, base, _ := Shell(c, func() *ui.Element {
 		return ui.Box(c).Focusable().Role(ui.RoleTextField).Label(o.Label).Disabled(o.Disabled)
 	})
@@ -58,7 +64,7 @@ func Editor(c *ui.Context, value *string, o EditorOptions) Edit {
 		base.Description(*value)
 	}
 	width, check := WrapWidth(c, shell)
-	env := editEnv{multi: o.Multiline, maxLen: o.MaxLength, mask: o.Mask, width: width, dot: k.dot, read: c.ReadClipboard, write: c.WriteClipboard}
+	env := editEnv{multi: o.Multiline, sends: o.EnterSends, maxLen: o.MaxLength, mask: o.Mask, width: width, dot: k.dot, read: c.ReadClipboard, write: c.WriteClipboard}
 	shown := s.view(o.Mask, true)
 	caret := s.caret + s.composeCaret
 	lines := editLayout(shown, width, o.Multiline)
@@ -403,7 +409,8 @@ func (s *editState) key(ev ui.InputEvent, e editEnv) bool {
 			s.eraseOr(s.caret, s.caret+1)
 		}
 	case ui.KeyEnter:
-		if !e.multi || m != 0 {
+		brk := e.multi && m == 0 && (shift || !e.sends)
+		if !brk {
 			s.submitted = true
 			return true
 		}