Make the kiosk autologin survive a reboot, and allow forcing a display mode

Two problems on musicdolphin, found after its first reboot.

getty@tty1 was never enabled. The role installed the autologin drop-in and the
handler restarted the unit, which works until the next boot - these images do
not enable getty@tty1 themselves, getty.target pulls in getty-static.service and
nothing else, so after a reboot nobody logs in and the kiosk never starts. Enable
it as well as starting it.

And the attached screen reads back 0 bytes of EDID on both micro-HDMI ports while
reporting "disconnected", so the kernel offers no modes, no framebuffer is
created, and X exits with "no screens found". That is the signature of a cable or
adapter whose DDC/HPD lines are broken but whose video pairs are fine. Forcing
the connector on is not enough on its own - with no EDID there is still no mode
to set - so allow a `video=` kernel parameter, which forces the output and names
the mode. hdmi_force_hotplug=1 is no use here; vc4-kms-v3d ignores it.

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

host_vars/musicdolphin.yml

@@ -16,3 +16,8 @@ mediapi_has_dhtsensor: true
 mediapi_install_kidsmusic: true
 mediapi_has_monitor: true
 musicmouse_version: deploy/musicdolphin
+
+# The attached screen reads back 0 bytes of EDID on both micro-HDMI ports and reports
+# "disconnected", so the kernel offers no modes and X dies with "no screens found".
+# Force the mode instead. Use the port nearest the USB-C jack (HDMI0 = HDMI-A-1).
+pi_kiosk_force_mode: "HDMI-A-1:1920x1080@60e"