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>

tabletop/mahjongtile.go

@@ -51,7 +51,7 @@ var (
 const tileW, tileH = 26, 34
 
 // MahjongTile is a suit or honor tile, or its back.
-func MahjongTile(c *ui.Context, t Tile, o MahjongTileOptions) *ui.Element {
+func MahjongTile(c *ui.Context, t Tile, o MahjongTileOptions) ui.Element {
 	k := pixel.K(c)
 	if t.Family < Dots || t.Family > Dragons || t.Rank < 1 || t.Rank > families[t.Family].ranks {
 		panic(fmt.Sprintf("tabletop: MahjongTile %+v", t))