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>

THIRD_PARTY_NOTICES.md

@@ -4,7 +4,7 @@
 
 | Work | Version | License | What it does here |
 | --- | --- | --- | --- |
-| [MyGo](https://github.com/egoist/mygo) | v0.2.10 | MIT | Native UI toolkit the components build on |
+| [MyGo](https://github.com/egoist/mygo) | v0.5.5 | MIT | Native UI toolkit the components build on |
 | [Ark Pixel Font](https://github.com/TakWolf/ark-pixel-font), 12px proportional zh_Hans | 2026.09.25 | SIL OFL 1.1 | The pixel font, packed into `pixel/font12.bin` |
 | [rsc.io/qr](https://pkg.go.dev/rsc.io/qr) | v0.2.0 | BSD-3-Clause | QR encoding for `display.QRCode` |
 | [go-text/typesetting](https://github.com/go-text/typesetting) | v0.3.5 | Unlicense or BSD-3-Clause; used under BSD-3-Clause | Text shaping inside MyGo |