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/split_test.go

@@ -0,0 +1,131 @@
+package layout
+
+import (
+	"testing"
+	"time"
+
+	"git.zacharyzhang.com/ZacharyZhang-NY/CrychicUI/sound"
+	"github.com/egoist/mygo/ui"
+)
+
+func TestSplitPaneDrags(t *testing.T) {
+	size, changes := float32(100), 0
+	tt := ui.NewTester(func(c *ui.Context) {
+		if SplitPane(c, &size, func() { ui.Text(c, "Left") }, func() { ui.Text(c, "Right") }).Changed() {
+			changes++
+		}
+	}, 400, 200)
+	ticks := count(sound.Tick)
+	tt.Press(104, 100)
+	tt.Move(130, 100)
+	tt.Move(154, 100)
+	tt.Release(154, 100)
+	if size != 150 || changes == 0 || count(sound.Tick) != ticks+1 {
+		t.Errorf("size %v, changes %d, ticks %d", size, changes, count(sound.Tick)-ticks)
+	}
+	if x := find(t, tt, "Right").X; x < 150 {
+		t.Errorf("right pane at %v", x)
+	}
+	tt.Press(154, 100)
+	tt.Move(100, 100)
+	tt.Move(-50, 100)
+	tt.Release(-50, 100)
+	if size != minPane {
+		t.Errorf("size %v, want clamp to %d", size, minPane)
+	}
+	panics(t, "nil size", func() { ui.Render(func(c *ui.Context) { SplitPane(c, nil, nil, nil) }, 10, 10, 1) })
+}
+
+func TestSplitStackDrags(t *testing.T) {
+	size := float32(80)
+	tt := ui.NewTester(func(c *ui.Context) {
+		SplitStack(c, &size, func() { ui.Text(c, "Top") }, func() { ui.Text(c, "Bottom") })
+	}, 300, 300)
+	ticks := count(sound.Tick)
+	tt.Press(150, 84)
+	tt.Move(150, 120)
+	tt.Move(150, 144)
+	tt.Release(150, 144)
+	if size != 140 || count(sound.Tick) != ticks+1 {
+		t.Errorf("size %v, ticks %d", size, count(sound.Tick)-ticks)
+	}
+	tt.Press(150, 144)
+	tt.Move(150, 400)
+	tt.Move(150, 600)
+	tt.Release(150, 600)
+	if want := 300 - 8 - float32(minPane); size != want {
+		t.Errorf("size %v, want clamp to %v", size, want)
+	}
+}
+
+func TestSidebarLayoutToggles(t *testing.T) {
+	open, changes := true, 0
+	tt := ui.NewTester(func(c *ui.Context) {
+		if SidebarLayout(c, &open, func() { ui.Text(c, "Side") }, func() { ui.Text(c, "Main") }).Changed() {
+			changes++
+		}
+	}, 600, 300)
+	before, toggles := find(t, tt, "Main").X, count(sound.Toggle)
+	if err := tt.Click("Toggle sidebar"); err != nil {
+		t.Fatal(err)
+	}
+	if open || changes != 1 || count(sound.Toggle) != toggles+1 {
+		t.Errorf("open %v, changes %d, toggles %d", open, changes, count(sound.Toggle)-toggles)
+	}
+	tt.Advance(80 * time.Millisecond)
+	mid := find(t, tt, "Main").X
+	settles(t, tt, "SidebarLayout width")
+	if after := find(t, tt, "Main").X; !(before > mid && mid > after) {
+		t.Errorf("main did not slide: %v, %v, %v", before, mid, after)
+	}
+	panics(t, "nil open", func() { ui.Render(func(c *ui.Context) { SidebarLayout(c, nil, nil, nil) }, 10, 10, 1) })
+}
+
+func TestSplitPaneStillPressIsNoChange(t *testing.T) {
+	size, changes := float32(100), 0
+	tt := ui.NewTester(func(c *ui.Context) {
+		if SplitPane(c, &size, func() { ui.Text(c, "Left") }, func() { ui.Text(c, "Right") }).Changed() {
+			changes++
+		}
+	}, 400, 200)
+	for range 3 {
+		tt.Press(104, 100)
+		tt.Frame()
+		tt.Release(104, 100)
+	}
+	if size != 100 || changes != 0 {
+		t.Errorf("still presses: size %v, %d changes", size, changes)
+	}
+}
+
+func TestSplitPaneNarrowKeepsMinimum(t *testing.T) {
+	size := float32(minPane)
+	tt := ui.NewTester(func(c *ui.Context) {
+		SplitPane(c, &size, func() {}, func() {})
+	}, 60, 100)
+	tt.Press(44, 50)
+	tt.Move(50, 50)
+	tt.Release(50, 50)
+	if size != minPane {
+		t.Errorf("size %v, want %d", size, minPane)
+	}
+}
+
+func TestSplitStackKeepsCallerKey(t *testing.T) {
+	order, ids := []string{"a", "b"}, map[string]uint64{}
+	sizes := map[string]*float32{"a": new(float32(60)), "b": new(float32(60))}
+	tt := ui.NewTester(func(c *ui.Context) {
+		ui.Column(c).Fill().Children(func() {
+			for _, k := range order {
+				c.Key(k)
+				ids[k] = SplitStack(c, sizes[k], func() {}, func() {}).ID()
+			}
+		})
+	}, 300, 300)
+	a, b := ids["a"], ids["b"]
+	order = []string{"b", "a"}
+	tt.Frame()
+	if ids["a"] != a || ids["b"] != b {
+		t.Errorf("ids moved with order: a %d→%d, b %d→%d", a, ids["a"], b, ids["b"])
+	}
+}