Keep the firmware reboot marker destination fixed

A caller-controlled marker path would let the privileged install command replace an unrelated file. Keep the production path fixed and redirect that literal only in isolated test copies. Cover hostile environment overrides without touching system files.

Co-Authored-By: GPT-6.1-Sol <noreply@openai.com>

Co-Authored-By: Greptile <165735046+greptile-apps[bot]@users.noreply.github.com>

migrations/1790904845.sh

@@ -4,7 +4,7 @@ if omarchy-hw-dell-xps13-dx13260-ptl; then
   source "$OMARCHY_PATH/install/hardware/dell-xps13-ptl-speaker-firmware.sh"
 
   # The marker lasts until reboot so every user migrating beforehand is prompted.
-  firmware_pending="${OMARCHY_XPS13_FIRMWARE_PENDING:-/run/omarchy/xps13-ptl-speaker-firmware}"
+  firmware_pending="/run/omarchy/xps13-ptl-speaker-firmware"
   if [[ -e $firmware_pending ]]; then
     omarchy-state set reboot-required
   fi