Fake Frame on arm64: use Valve's Holo Core image, and show failed builds

The menci/archlinuxarm base failed `pacman -Syu` on GitHub's arm64 runner.
Valve's Holo Core aarch64 preview is the base the Frame's SteamOS is built on,
the iPhone app's frame-container already uses it, and its repos carry every
package the fake needs. A failed image build now reruns with the full log.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

docs/testing.md

@@ -48,7 +48,7 @@ its guards want.
 
 | On the fake Frame | |
 |---|---|
-| Arch Linux (`archlinux:base`, or `menci/archlinuxarm:base` on arm64), user `steamos`, `/etc/os-release` with BUILD_ID 20260922.6101926 | Real OS, Frame's identity |
+| Arch Linux (`archlinux:base`, or Valve's Holo Core aarch64 preview on arm64), user `steamos`, `/etc/os-release` with BUILD_ID 20260922.6101926 | Real OS, Frame's identity |
 | `sshd` with key and password logins, `rsync`, `python3` | Real |
 | Valve's steamos-devkit-service on port 32000 and its hooks, vendored unmodified in `tests/fakeframe/steamos-devkit-service` | Real; only its `dbus` import (for mDNS through systemd-resolved) is a stand-in that logs the registration |
 | Valve's devkit-utils, copied over by Frame Control itself | Real |

scripts/e2e.sh

@@ -6,7 +6,7 @@
 # harness itself didn't come up). See docs/testing.md.
 #
 # Usage: scripts/e2e.sh [TEST...]     e.g. scripts/e2e.sh test_titles test_faults.Faults.test_disk_full
-# Env:   FAKEFRAME_BASE   base image (default: archlinux:base, or menci/archlinuxarm:base on arm64)
+# Env:   FAKEFRAME_BASE   base image (default: archlinux:base, or Valve's Holo Core aarch64 on arm64)
 #        FAKEFRAME_KEEP=1 leave the containers running afterwards
 set -uo pipefail
 
@@ -14,7 +14,7 @@ root=${0:A:h:h}
 cd "$root" || exit 2
 case $(uname -m) in
   x86_64|amd64) base=archlinux:base ;;
-  aarch64|arm64) base=menci/archlinuxarm:base ;;
+  aarch64|arm64) base=registry.gitlab.steamos.cloud/holo/holo-core-aarch64-preview/base-devel:latest ;;
   *) print -u2 "No Arch Linux base image known for $(uname -m); set FAKEFRAME_BASE"; exit 2 ;;
 esac
 base=${FAKEFRAME_BASE:-$base}
@@ -22,8 +22,10 @@ compose=(docker compose -p fakeframe-e2e -f tests/fakeframe/compose.yaml)
 started=$SECONDS
 
 print "==> Building fakeframe-frame (from $base) and fakeframe-host"
-docker build -q --build-arg BASE="$base" -t fakeframe-frame -f tests/fakeframe/Containerfile tests/fakeframe || exit 2
-docker build -q -t fakeframe-host -f tests/fakeframe/host.Containerfile tests/fakeframe || exit 2
+# Quiet when it works; if a build fails, build again with the full log so CI shows why.
+build() { docker build -q "$@" >/dev/null || { docker build --progress=plain "$@"; exit 2 } }
+build --build-arg BASE="$base" -t fakeframe-frame -f tests/fakeframe/Containerfile tests/fakeframe
+build -t fakeframe-host -f tests/fakeframe/host.Containerfile tests/fakeframe
 
 logs() {
   print "\n==> Fake Frame logs"

tests/fakeframe/Containerfile

@@ -2,8 +2,10 @@
 # Valve's steamos-devkit-service and hooks, a fake Steam client and stubs for
 # the Frame-only commands Frame Control runs. See docs/testing.md.
 #
-# BASE: archlinux:base on x86_64, menci/archlinuxarm:base on arm64 (a daily
-# Arch Linux ARM build); scripts/e2e.sh picks one from `uname -m`.
+# BASE: archlinux:base on x86_64; on arm64, Valve's Holo Core aarch64 preview
+# (registry.gitlab.steamos.cloud/holo/holo-core-aarch64-preview/base-devel), the
+# Arch Linux ARM64 port the Frame's SteamOS is built on (docs/recovery-and-images.md).
+# scripts/e2e.sh picks one from `uname -m`.
 ARG BASE=archlinux:base
 FROM ${BASE}