fix(wslg): boot-time X11 socket symlink + start user@1000.service

* usr/lib/tmpfiles.d/mios-wslg.conf (new): `L+ /tmp/.X11-unix - - -
  - /mnt/wslg/.X11-unix` -- forces the X11 socket symlink at BOOT
  via systemd-tmpfiles, instead of the previous shell-only `ln -sf`
  in /usr/lib/profile.d/mios-wsl2.sh which only ran when an
  interactive shell sourced profile. System-launched processes
  (Quadlets, .desktop launchers, dbus-activated services, GUI apps
  spawned by `nautilus &`) start without shell profile and hit:
    F: X11 socket /tmp/.X11-unix/X0 does not exist in filesystem.
    libportal-CRITICAL: Cannot autolaunch D-Bus without X11 $DISPLAY
  `L+` forces the symlink even if /tmp/.X11-unix already exists as
  an empty dir (some distro layers pre-create it that way and block
  a regular `ln -sf`). No-op on bare-metal hosts because /mnt/wslg
  doesn't exist there; tmpfiles silently skips L-rules with absent
  source.

* usr/lib/systemd/system/mios-wsl-runtime-dir.service: ExecStart now
  also drops /var/lib/systemd/linger/mios (canonical logind linger
  marker -- though logind itself is condition-gated off on WSL) and
  runs `systemctl start user@1000.service`. systemd-logind would
  normally start the user manager from the linger marker, but on WSL
  with logind absent we have to kick it ourselves. Without this the
  user D-Bus session bus never starts and GTK apps fail with
  `Cannot autolaunch D-Bus without X11 $DISPLAY` even when DISPLAY
  is correctly set. Failures are non-fatal -- the unit still
  succeeds even if user@<uid>.service can't fully come up, so the
  /run/user/$uid bit (the original purpose of the service) always
  lands.

Pairs with the existing user@1000.service preset entry in
90-mios.preset (added earlier to address the same "no user systemd
manager" issue from the operator's first WSL boot journal).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: Kabuki94

usr/lib/systemd/system/mios-wsl-runtime-dir.service

@@ -24,7 +24,9 @@ RemainAfterExit=yes
 ExecStart=/bin/bash -c '\
     getent passwd mios >/dev/null 2>&1 || exit 0; \
     UID_=$(id -u mios); GID_=$(id -g mios); \
-    install -d -m 0700 -o "$UID_" -g "$GID_" "/run/user/$UID_"'
+    install -d -m 0700 -o "$UID_" -g "$GID_" "/run/user/$UID_"; \
+    : > "/var/lib/systemd/linger/mios" 2>/dev/null || true; \
+    systemctl start "user@$UID_.service" 2>/dev/null || true'
 
 [Install]
 WantedBy=multi-user.target

usr/lib/tmpfiles.d/mios-wslg.conf

@@ -0,0 +1,24 @@
+# /usr/lib/tmpfiles.d/mios-wslg.conf
+#
+# Boot-time WSLg substrate wiring. Replaces the per-shell `ln -sf` in
+# /usr/lib/profile.d/mios-wsl2.sh which only ran when an interactive
+# shell sourced profile -- system-launched processes (Quadlets, GUI
+# apps spawned via .desktop launcher, dbus-activated services) start
+# WITHOUT shell profile and missed the symlink, so they hit:
+#
+#     F: X11 socket /tmp/.X11-unix/X0 does not exist in filesystem.
+#     dbind-WARNING: Could not open X display
+#     libportal-CRITICAL: Cannot autolaunch D-Bus without X11 $DISPLAY
+#
+# `L+` forces the symlink even if /tmp/.X11-unix already exists (some
+# distros pre-create it as an empty dir at boot, blocking the symlink
+# the profile.d script tried to make later). Targets /mnt/wslg/ which
+# WSL2 mounts unconditionally on every distro with guiApplications=true
+# in .wslconfig (set by the MiOS bootstrap).
+#
+# No-op on bare-metal / Hyper-V / QEMU MiOS hosts because /mnt/wslg/
+# doesn't exist there; tmpfiles silently skips C-/L-rules whose source
+# paths are absent.
+
+# /tmp/.X11-unix -> /mnt/wslg/.X11-unix (X11 socket directory)
+L+ /tmp/.X11-unix - - - - /mnt/wslg/.X11-unix