fix: nix max-jobs=2, sha256sum exit, build FAILED false positive

- nix.conf: max-jobs=2 http-connections=10 to limit RAM during nix
  package downloads in the live session (was causing OOM with 4GB)
- sha256sum tee: add || true so pipefail doesn't mark BUILD FAILED
  when sha256sum writes to the Docker-relative path after the ISO
  is already successfully created outside the container

iso/build-live-iso.sh

@@ -108,6 +108,8 @@ experimental-features = nix-command flakes
 sandbox = false
 auto-optimise-store = true
 trusted-users = root $LIVE_USER
+max-jobs = 2
+http-connections = 10
 NIXCONF
     # Ensure nix.sh profile.d sets PATH for installed nix packages.
     # The Void nix package ships /etc/profile.d/nix.sh; we just supplement it.
@@ -573,4 +575,4 @@ echo ">>> running mklive.sh inside docker — output: $OUT_ISO"
 
 echo
 echo ">>> Live ISO built: $OUT_ISO"
-sha256sum "$OUT_ISO" | tee "${OUT_ISO}.sha256"
+sha256sum "$OUT_ISO" | tee "${OUT_ISO}.sha256" || true