Upgrade MyGo to v0.5.5

Elements are now pass-scoped value handles: tests that read bounds
after a frame bind a ui.Handle. pixel tells frames apart by the build
pass's root, since the Tester clock no longer moves on its own.

Fix the regressions the upgrade brought:
- Clipboard reads in input handlers go through c.Services().
- MyGo notes an overlay's opener after building it, so AutoFocus
  inside lost it; pixel.AutoFocus focuses through a Handle, and
  archtest bans the raw call. Dialogs hand the focus back again.
- Elements around a press stay hovered: Tooltip tells a press-given
  focus by focus arriving under the pointer.
- The web host moves the Tester clock with real time, at most 500 ms
  a call, and gives components the real clock.

The gallery's source index also accepts CRLF checkouts.

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

fx/fx.go

@@ -10,7 +10,7 @@ import (
 )
 
 // box sizes an effect; a label makes it an image.
-func box(c *ui.Context, k pixel.Kit, label string, w, h int) *ui.Element {
+func box(c *ui.Context, k pixel.Kit, label string, w, h int) ui.Element {
 	e := ui.Box(c).Size(k.D(w), k.D(h))
 	if label != "" {
 		return e.Label(label).Role(ui.RoleImage)
@@ -87,7 +87,7 @@ func checkHour(name string, hour int) {
 }
 
 // cover draws over e's content, clipped to e.
-func cover(k pixel.Kit, e *ui.Element, draw func(g pixel.Canvas), content func()) *ui.Element {
+func cover(k pixel.Kit, e ui.Element, draw func(g pixel.Canvas), content func()) ui.Element {
 	return e.DrawOver(func(p *ui.Painter, r ui.Rect) {
 		g := k.Canvas(p, r)
 		g.Clip(0, 0, g.W, g.H, func() { draw(g) })