Fix remote input: give the compositor a libinput backend

The stream rendered but ignored keyboard and mouse. Sunshine injects input
through uinput exclusively — it has no support for the Wayland virtual
keyboard/pointer protocols — so the compositor has to have a libinput
backend to see those devices. WLR_BACKENDS=headless creates only the
headless backend, so sway had zero input devices against the kernel's 24.

libinput needs a seat, and a systemd --user service belongs to no logind
session, so libseat needs seatd. seatd is now enabled on this host.

Its socket defaults to group `seat`, which does not help here: the user
manager's group list is fixed when it starts, Linger=yes means that is at
boot, and so adding connor to `seat` would not take effect until a reboot —
re-logging in changes nothing. The drop-in points seatd at `video`, a group
connor already holds for GPU access, which makes this deterministic instead
of dependent on group-propagation timing.

sway now reports 7 input devices including libvirtualhid Mouse and
Keyboard, which are Sunshine's.

hosts/mainframe/etc/ is a new tree for system-level config; install flags
it the same way it flags sbin.

hosts/mainframe/etc/systemd/system/seatd.service.d/override.conf

@@ -0,0 +1,11 @@
+# seatd's socket defaults to group `seat`. The compositor runs as a systemd
+# --user service, and that manager's group list is fixed at the moment it
+# starts — with Linger=yes it starts at boot, so adding connor to `seat` does
+# not reach it until a reboot, and re-logging in changes nothing.
+#
+# `video` is a group connor already holds (it is required for GPU access
+# anyway), so pointing seatd at it makes seat access deterministic rather than
+# dependent on group-propagation timing.
+[Service]
+ExecStart=
+ExecStart=/usr/bin/seatd -g video

hosts/mainframe/systemd/sway-headless.service

@@ -5,8 +5,18 @@ ConditionHost=mainframe
 
 [Service]
 Type=simple
-# headless backend: no seat, no input devices, one virtual output.
+# headless for the virtual output, libinput so there is an input backend at
-Environment=WLR_BACKENDS=headless
+# all. With WLR_BACKENDS=headless alone wlroots creates no libinput backend,
+# so the compositor has zero input devices and Sunshine's uinput keyboard and
+# mouse are never picked up — the stream shows the desktop and ignores you.
+#
+# libinput needs a seat, and a systemd --user service sits in no logind
+# session, so libseat falls back to seatd. That is why seatd.service is enabled
+# on this host and connor is in the seat group.
+Environment=WLR_BACKENDS=headless,libinput
+Environment=LIBSEAT_BACKEND=seatd
+# Do not fail to start when no input device is present yet; Sunshine creates
+# its virtual ones only once a client connects.
 Environment=WLR_LIBINPUT_NO_DEVICES=1
 # Pin the compositor to the NVIDIA card (card0 = 01:00.0, renderD129), which is
 # also what sunshine.conf names as its encoder. Without this wlroots picks the

install

@@ -48,3 +48,8 @@ if [[ -d "hosts/${HOST}/sbin" ]] && [[ -n "$(ls -A "hosts/${HOST}/sbin" 2>/dev/n
   echo "note: this host has system scripts needing root:"
   echo "      sudo install -m755 hosts/${HOST}/sbin/* /usr/local/bin/"
 fi
+if [[ -d "hosts/${HOST}/etc" ]]; then
+  echo
+  echo "note: this host has system config needing root:"
+  echo "      sudo cp -r hosts/${HOST}/etc/. /etc/ && sudo systemctl daemon-reload"
+fi