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>

navigation/contextmenu.go

@@ -13,7 +13,7 @@ type ContextMenuOptions struct {
 }
 
 type ContextMenuResult struct {
-	Element *ui.Element
+	Element ui.Element
 	// Chosen is the item taken this frame, or -1.
 	Chosen int
 }
@@ -70,7 +70,7 @@ func ContextMenu(c *ui.Context, text string, items []MenuItem, o ContextMenuOpti
 	if clicked >= 0 {
 		res.Chosen = clicked
 	}
-	if panel != nil {
+	if panel.Valid() {
 		b := area.Bounds()
 		panel.Left(b.X + s.x).Top(b.Y + s.y)
 	}