Add procps to fix ps: command not found during self-update

Dockerfile

@@ -1,6 +1,6 @@
 # syntax=docker/dockerfile:1
 
 FROM --platform=linux/amd64 debian:trixie-slim
 
 ARG VERSION=dev
 ARG GIT_SHA=unknown
@@ -26,10 +26,11 @@
 #   libfreetype6    — provides libfreetype.so.6 soname that bundled libharfbuzz links against
 #   cifs-utils      — SMB/CIFS network share mounting
 #   ca-certificates — HTTPS for streaming services and cloud APIs
+#   procps          — provides ps, required by RoonServer's self-update script
 RUN apt-get update \
  && apt-get -y install --no-install-recommends \
     bash curl xz-utils bzip2 tzdata libicu76 \
-    libasound2t64 libfreetype6 cifs-utils ca-certificates \
+    libasound2t64 libfreetype6 cifs-utils ca-certificates procps \
  && (chmod u-s /usr/sbin/mount.cifs 2>/dev/null || true) \
  && apt-get clean \
  && rm -rf /var/lib/apt/lists/* /var/log/apt /var/log/dpkg.log \

tests/smoke.sh

@@ -40,6 +40,19 @@ for bin in bash curl bzip2 tar ffmpeg; do
         docker run --rm --entrypoint which "$IMAGE" "$bin"
 done
 
+# ps (procps) is a runtime contract: RoonServer's bundled self-update
+# launcher runs `ps -Awwo pid,args | grep '[R]AATServer' | awk ...` to
+# kill stale RAATServer processes. A missing procps silently breaks
+# updates (RRD-1551), so assert both the binary and that the pipeline runs.
+check "ps is available (procps — RoonServer self-update)" \
+    docker run --rm --entrypoint which "$IMAGE" ps
+
+# Exercise the exact flags the launcher uses. Checking ps's own exit code
+# (not the pipeline's) is deliberate: a missing/broken ps must fail here,
+# whereas the full pipeline's exit is awk's, which is 0 even when ps errors.
+check "ps self-update invocation runs (ps -Awwo pid,args)" \
+    docker run --rm --entrypoint ps "$IMAGE" -Awwo pid,args
+
 # FFmpeg is a static binary from johnvansickle.com — verify it actually
 # executes on this image's glibc/kernel ABI, not just that the file exists.
 check "ffmpeg runs (static binary ABI-compatible)" \