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>

chart/scatterplot.go

@@ -13,7 +13,7 @@ type ScatterPlotOptions struct {
 }
 
 // ScatterPlot puts each point as a 2×2 square.
-func ScatterPlot(c *ui.Context, text string, points []Point, o ScatterPlotOptions) *ui.Element {
+func ScatterPlot(c *ui.Context, text string, points []Point, o ScatterPlotOptions) ui.Element {
 	k := pixel.K(c)
 	w, h := size("ScatterPlot", o.Width, o.Height, 160, 80)
 	f := fitPoints(points, w, h, 2)