Add gallery app, native window and architecture tests

AGENTS.md

@@ -55,6 +55,7 @@ Imports point down only. Same-tier imports are forbidden. `internal/archtest` en
 - Signatures and results: PRD §5.1. Zero options give the default look. Sizes in options are dots.
 - `k := pixel.K(c)` once per component; layout sizes through `k.D(n)`.
 - Row builders that MyGo runs during layout (`List`, `GridView`, `Outline`) go through `pixel.Lazy(c, row)`.
+- Single-key shortcuts only while `pixel.Typing(c)` is false; MyGo routes shortcuts before a focused field.
 - Copy shown by a component comes from `k.Msg`; business copy comes from the caller.
 - Fail fast: panic on programmer errors such as bad options. Never swallow an error.
 - Composites log state changes: `slog.Debug("8bit: <component> <event>", …)`. Never log secrets.