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>

input/checkbox.go

@@ -26,7 +26,7 @@ type CheckboxOptions struct {
 }
 
 type CheckboxResult struct {
-	Element *ui.Element
+	Element ui.Element
 	Changed bool
 }
 
@@ -35,7 +35,7 @@ func Checkbox(c *ui.Context, text string, checked *bool, o CheckboxOptions) Chec
 	k := pixel.K(c)
 	// The base turns before it learns it is off.
 	on := *checked
-	shell, base, st := pixel.Shell(c, func() *ui.Element { return ui.CheckboxBase(c, &on).Label(text).Disabled(o.Disabled) })
+	shell, base, st := pixel.Shell(c, func() ui.Element { return ui.CheckboxBase(c, &on).Label(text).Disabled(o.Disabled) })
 	changed := on != *checked && !base.IsDisabled()
 	if changed {
 		*checked = on