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.

chat/attachmentchip.go

@@ -0,0 +1,72 @@
+package chat
+
+import (
+	"fmt"
+	"log/slog"
+	"path/filepath"
+	"strings"
+
+	"github.com/egoist/mygo/ui"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/display"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/icon"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/input"
+	"git.zacharyzhang.com/ZacharyZhang-NY/8bitMyGoUI/pixel"
+)
+
+type AttachmentChipOptions struct {
+	// Width caps the name in dots; zero means 100.
+	Width    int
+	Disabled bool
+}
+
+type AttachmentChipResult struct {
+	Element *ui.Element
+	Removed bool
+}
+
+// kinds pick a file's icon by its extension.
+var kinds = map[string]*pixel.Sprite{
+	".png": icon.Image, ".jpg": icon.Image, ".gif": icon.Image, ".mp3": icon.Music, ".wav": icon.Music, ".ogg": icon.Music,
+	".mp4": icon.Video, ".mov": icon.Video, ".go": icon.Code, ".js": icon.Code, ".py": icon.Code,
+	".txt": icon.FileText, ".md": icon.FileText, ".pdf": icon.FileText,
+}
+
+// AttachmentChip shows a file's icon, name, size and ×.
+func AttachmentChip(c *ui.Context, name string, size int64, o AttachmentChipOptions) AttachmentChipResult {
+	k := pixel.K(c)
+	if size < 0 {
+		panic(fmt.Sprintf("chat: attachment %q has size %d", name, size))
+	}
+	sp, ok := kinds[strings.ToLower(filepath.Ext(name))]
+	if !ok {
+		sp = icon.File
+	}
+	var res AttachmentChipResult
+	res.Element = ui.Row(c).Gap(k.D(3)).Padding(k.D(2), k.D(2), k.D(2), k.D(4)).AlignItems(ui.Center).Draw(func(p *ui.Painter, r ui.Rect) {
+		g := k.Canvas(p, r)
+		g.Frame(0, 0, g.W, g.H, pixel.Notched, pixel.Face)
+	}).Children(func() {
+		display.Icon(c, sp, display.IconOptions{Slot: pixel.Faint})
+		pixel.Text(c, line(name, pixel.Or("AttachmentChip Width", o.Width, 100)), pixel.TextOptions{})
+		pixel.Text(c, bytes(size), pixel.TextOptions{Slot: pixel.Faint})
+		if input.IconButton(c, icon.Close, k.Msg("remove")+" "+name, input.IconButtonOptions{Variant: input.Ghost, Size: input.Small, Disabled: o.Disabled}).Clicked {
+			res.Removed = true
+			slog.Debug("8bit: attachment removed", "name", name)
+		}
+	})
+	return res
+}
+
+// bytes prints n in binary units, tenths below ten.
+func bytes(n int64) string {
+	v, units := float64(n), []string{"B", "KB", "MB", "GB", "TB"}
+	i := 0
+	for v >= 1024 && i < len(units)-1 {
+		v, i = v/1024, i+1
+	}
+	if i > 0 && v < 10 {
+		return fmt.Sprintf("%.1f %s", v, units[i])
+	}
+	return fmt.Sprintf("%.0f %s", v, units[i])
+}