Add layout components 0001-0025

Stack through StickyHeader, with behavior tests and gallery demos.
kit gains Arrive, Settle (paint-time layout check) and Shade.
Several actions return named ui.Element results; mygo vet forbids
elements in structs.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

layout/app_frame.go

@@ -0,0 +1,22 @@
+package layout
+
+import (
+	"time"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/CrychicUI/kit"
+	"github.com/egoist/mygo/ui"
+)
+
+// AppFrame stacks top bar, content, status bar; bars slide.
+func AppFrame(c *ui.Context, top, content, status func()) ui.Element {
+	t := c.Theme()
+	return ui.Column(c).Fill().Children(func() {
+		bar := ui.Row(c).FillWidth().Gap(t.Space(3)).Padding(t.Space(2), t.Space(4)).AlignItems(ui.Center)
+		kit.Arrive(bar, ui.Pose{Y: -8, Fade: 1}, 0).Children(top)
+		ui.Divider(c)
+		ui.Column(c).Grow(1).Children(content)
+		ui.Divider(c)
+		foot := ui.Row(c).FillWidth().Gap(t.Space(3)).Padding(t.Space(1.5), t.Space(4)).AlignItems(ui.Center)
+		kit.Arrive(foot, ui.Pose{Y: 8, Fade: 1}, 80*time.Millisecond).Children(status)
+	})
+}