fix: steamify-install mounts the new system's /var/log (@log) first, so its logs aren't hidden under the mount after boot

CHANGELOG.md

@@ -56,6 +56,9 @@ CachyOS 26.08 with Steamify built in: install CachyOS and turn the PC into a Ste
   `steamify-install` now registers it with `efibootmgr` from the live system, with the ESP's real
   disk and partition (bootctl in the chroot writes an entry without a partition, which the firmware
   can't load); the output is in `/var/log/steamify-bootentry.log`
+* **Installer:** Steamify's install-time logs (`/var/log/steamify-install.log`,
+  `steamify-bootentry.log`) are readable after the first boot: `/var/log` is its own btrfs subvolume
+  (`@log`) that wasn't mounted yet when Steamify ran, so they ended up hidden under it
 * **Installer:** Steamify's setup never asks for a password (its sudo rule is read after CachyOS's
   `%wheel` rule); Calamares starts with the Boost version it was linked against
 * **Build:** finishes cleanly as root and reports no error after a successful build; the Steamify page's

archiso/airootfs/usr/local/bin/steamify-install

@@ -20,6 +20,17 @@ for id in ${choice//,/ }; do
         *) options+="${options:+,}$id" ;;
     esac
 done
+# /var/log is its own btrfs subvolume (@log) that the installer doesn't mount at $root/var/log: what is
+# written there now (these logs, Steamify's) would end up hidden under the mount after boot. Mount it
+# from the new system's fstab for this run.
+mounted_log=false
+if [[ -n "$root" && -d "$root/var/log" ]] && ! mountpoint -q "$root/var/log"; then
+    read -r dev _ _ opts _ < <(awk '$2 == "/var/log" && $1 !~ /^#/' "$root/etc/fstab" 2>/dev/null)
+    if [[ -n "${dev:-}" ]] && mount -o "$opts" "$dev" "$root/var/log" 2>/dev/null; then
+        mounted_log=true
+        trap '$mounted_log && umount "$root/var/log"' EXIT
+    fi
+fi
 # systemd-boot: cachyos-installer runs `bootctl install` in a chroot, and bootctl leaves the EFI
 # variables alone there: no "Linux Boot Manager" boot entry, so the firmware tries the network and
 # its other entries first and finds the disk's fallback path last (or never). bootctl can't be made