fix: raise sunshine fd limit

It leaks a /dev/dri/renderD fd per encoder probe, hits the 1024 default,
and mesa can then no longer dlopen the GBM driver — capture degrades to a
black picture with no error surfaced.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

hosts/common/features/remote-desktop.nix

@@ -5,6 +5,12 @@ _:
 #
 # First run: https://<host>:47990 to set web-UI credentials, then pair Moonlight.
 {
+  # Sunshine opens /dev/dri/renderD* once per encoder probe and never closes
+  # them — ~973 fds against the 1024 default. Mesa then cannot dlopen the GBM
+  # driver ("Too many open files"), capture falls back to a broken path, and
+  # moonlight shows a black, artefacted picture rather than any error.
+  systemd.user.services.sunshine.serviceConfig.LimitNOFILE = 65536;
+
   services.sunshine = {
     enable = true;
     autoStart = true;