feat(packaging): a desktop-login host restarts with its desktop

The shipped unit's PartOf=punktfunk-kde-session.service covers the
APPLIANCE route, where we start the compositor ourselves. A host on a
machine somebody logs into has no such unit: when Plasma or GNOME
restarts, the daemon keeps running while holding a Wayland socket and a
portal D-Bus connection that both died with the old compositor, and it
cannot recover either in-process. It fails quietly — the host still
listens, still answers, and every session it then serves dies at capture.
A host that mirrors a monitor idles for days between sessions, which is
the shape that finds this at the worst moment.

The drop-in binds the host to graphical-session.target: PartOf takes it
down with the session, WantedBy brings it back with the new one. Shipped
under /usr/share rather than as an active drop-in, because it is wrong
for the appliance route (which may never reach that target at all, and
would then leave the host permanently stopped) — the operator opts in.

Closes the restart half of design/per-monitor-portal-capture.md §6.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

packaging/arch/PKGBUILD

@@ -161,6 +161,12 @@ package_punktfunk-host() {
   install -Dm0644 "$R/scripts/punktfunk-host.service" "$pkgdir/usr/lib/systemd/user/punktfunk-host.service"
   sed -i 's#%h/punktfunk/target/release/punktfunk-host#/usr/bin/punktfunk-host#' \
     "$pkgdir/usr/lib/systemd/user/punktfunk-host.service"
+  # Optional drop-in for a DESKTOP-LOGIN host: binds the host to graphical-session.target so a
+  # Plasma/GNOME restart restarts it instead of leaving it on a dead compositor connection. Shipped
+  # under /usr/share (NOT as an active drop-in) because it is wrong for the appliance route — the
+  # operator copies it into ~/.config/systemd/user/punktfunk-host.service.d/ when they want it.
+  install -Dm0644 "$R/scripts/punktfunk-host-desktop-session.conf" \
+    "$pkgdir/usr/share/punktfunk/punktfunk-host-desktop-session.conf"
   install -Dm0644 "$R/scripts/punktfunk-kde-session.service" "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service"
   sed -i 's#%h/punktfunk/scripts/headless/run-headless-kde.sh#/usr/share/punktfunk/headless/run-headless-kde.sh#' \
     "$pkgdir/usr/lib/systemd/user/punktfunk-kde-session.service"

packaging/debian/build-deb.sh

@@ -67,6 +67,12 @@ install -Dm0644 scripts/punktfunk-host.service     "$STAGE/usr/lib/systemd/user/
 # /usr/bin. Rewrite it so a fresh apt install (no hand-rolled unit) starts the installed binary.
 sed -i 's#%h/punktfunk/target/release/punktfunk-host#/usr/bin/punktfunk-host#' \
     "$STAGE/usr/lib/systemd/user/punktfunk-host.service"
+# Optional drop-in for a DESKTOP-LOGIN host: binds the host to graphical-session.target so a
+# Plasma/GNOME restart restarts it instead of leaving it on a dead compositor connection. Shipped
+# under /usr/share (NOT as an active drop-in) because it is wrong for the appliance route — the
+# operator copies it into ~/.config/systemd/user/punktfunk-host.service.d/ when they want it.
+install -Dm0644 scripts/punktfunk-host-desktop-session.conf \
+    "$STAGE/usr/share/punktfunk-host/punktfunk-host-desktop-session.conf"
 # Optional headless KWin session unit (the kwin --virtual appliance), as the RPM/Arch ship.
 # Repoint its ExecStart from the dev source tree to the packaged script. NOT enabled by default.
 install -Dm0644 scripts/punktfunk-kde-session.service "$STAGE/usr/lib/systemd/user/punktfunk-kde-session.service"

packaging/rpm/punktfunk.spec

@@ -284,6 +284,11 @@ install -Dm0644 scripts/punktfunk-host.service %{buildroot}%{_userunitdir}/punkt
 # The source unit's ExecStart points at the dev source tree; a packaged install has the binary at
 # %{_bindir}. Rewrite it so a fresh install (no hand-rolled unit) starts the installed binary.
 sed -i 's#%h/punktfunk/target/release/punktfunk-host#%{_bindir}/punktfunk-host#' %{buildroot}%{_userunitdir}/punktfunk-host.service
+# Optional drop-in for a DESKTOP-LOGIN host: binds the host to graphical-session.target so a
+# Plasma/GNOME restart restarts it instead of leaving it on a dead compositor connection. Shipped
+# under %{_datadir}/%{name} (NOT as an active drop-in) because it is wrong for the appliance route —
+# the operator copies it into ~/.config/systemd/user/punktfunk-host.service.d/ when they want it.
+install -Dm0644 scripts/punktfunk-host-desktop-session.conf %{buildroot}%{_datadir}/%{name}/punktfunk-host-desktop-session.conf
 
 # Optional headless KDE session unit (the kwin streaming appliance): brings up `kwin --virtual` on
 # wayland-kde via the packaged run-headless-kde.sh, so the host's kwin backend has a session whose