feat(iso): add optional kms display boot path

iso/overlay/etc/systemd/system/lightdm.service.d/bee-display-mode.conf

@@ -0,0 +1,6 @@
+[Unit]
+Wants=bee-preflight.service
+After=bee-preflight.service
+
+[Service]
+ExecStartPre=/usr/local/bin/bee-display-mode

iso/overlay/usr/local/bin/bee-display-mode

@@ -0,0 +1,54 @@
+#!/bin/sh
+# Select Xorg display mode based on kernel cmdline.
+# Default is the current server-safe path: keep forced fbdev.
+set -eu
+
+cmdline_param() {
+    key="$1"
+    for token in $(cat /proc/cmdline 2>/dev/null); do
+        case "$token" in
+            "$key"=*)
+                echo "${token#*=}"
+                return 0
+                ;;
+        esac
+    done
+    return 1
+}
+
+log() {
+    echo "bee-display-mode: $*"
+}
+
+mode="$(cmdline_param bee.display || true)"
+if [ -z "$mode" ]; then
+    mode="safe"
+fi
+
+xorg_dir="/etc/X11/xorg.conf.d"
+fbdev_conf="${xorg_dir}/10-fbdev.conf"
+fbdev_park="${xorg_dir}/10-fbdev.conf.disabled"
+
+mkdir -p "$xorg_dir"
+
+case "$mode" in
+    kms|auto)
+        if [ -f "$fbdev_conf" ]; then
+            mv "$fbdev_conf" "$fbdev_park"
+            log "mode=${mode}; disabled forced fbdev config"
+        else
+            log "mode=${mode}; fbdev config already disabled"
+        fi
+        ;;
+    safe|fbdev|"")
+        if [ -f "$fbdev_park" ] && [ ! -f "$fbdev_conf" ]; then
+            mv "$fbdev_park" "$fbdev_conf"
+            log "mode=${mode}; restored forced fbdev config"
+        else
+            log "mode=${mode}; keeping forced fbdev config"
+        fi
+        ;;
+    *)
+        log "unknown bee.display=${mode}; keeping forced fbdev config"
+        ;;
+esac