Added a fix for X11 / Cinnamon window popups and maximize button not visible.

ptlinux/native/gamescope-compat.README

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+Gamescope compatibility binary
+================================
+
+gamescope-3.16.20-ubuntu26.04-amd64 is an isolated compatibility build for
+Ubuntu 26.04 amd64. The launcher uses it only when the installed system
+Gamescope reports version 3.16.20 and the binary passes its embedded SHA-256
+check. It never replaces /usr/games/gamescope.
+
+Source package:
+  Ubuntu gamescope 3.16.20+ds-1
+  gamescope_3.16.20+ds.orig.tar.xz
+  SHA-256 a27984fdab2bbfe353efc772de214ae88cccab07c4507747ed4b7f063b2faa0e
+  gamescope_3.16.20+ds-1.debian.tar.xz
+  SHA-256 ae6e9bac39b576e7d9c15912a713796049a29756f6858364ef49bd02197cb153
+
+Build:
+  ubuntu:26.04 container
+  apt-get build-dep gamescope
+  DEB_BUILD_OPTIONS=nocheck dpkg-buildpackage --build=binary --no-sign -jauto
+
+The source changes are:
+
+  gamescope-wayland-letterbox-backing.patch
+    Backports upstream commit 66450376038864700f9b4721343b4d15b29c4198
+    ("Use a backing surface for letter-boxing"). It fixes direct Wayland
+    output when a unity-scaled game surface has a nonzero letterbox offset.
+
+  gamescope-wayland-libdecor-input-scope.patch
+    Keeps libdecor titlebar and resize-border button events out of the nested
+    application while preserving complete button sequences that begin on the
+    game surface. This prevents a decoration operation from leaving the game
+    with a permanently held mouse button. It addresses the behavior tracked
+    at https://github.com/ValveSoftware/gamescope/issues/2299.
+
+  gamescope-lazy-output-images.patch
+    Backports upstream commit e383171ff1c0f7b5b37f05f2bb67f7c5282b087f
+    ("rendervulkan: make the shared output images on first use"). Direct
+    Wayland frames no longer allocate six output-sized Vulkan images at every
+    intermediate host-window size.
+
+  gamescope-wayland-live-resize.patch
+    Skips the remaining device-idle wait and transparent fallback-image rebuild
+    when direct Wayland presentation has no live output images. Full-composition
+    frames still allocate correctly sized images on demand.
+
+  gamescope-keep-nested-windows-visible.patch
+    Honors PTLINUX_GAMESCOPE_KEEP_WINDOWS_VISIBLE by rejecting the game's
+    login-transition iconify request. The outer desktop window retains its
+    normal size and visibility while host minimize and focus remain untouched.
+
+Binary SHA-256:
+  3fc81536c22dcce2c593c11507a612c13221f5b2ce2e5326f7c63706ca965639
+
+Licensing and copyright notices are in gamescope-compat.copyright.