fix(evals): build /run.sh with printf so legacy builder works

The Dockerfile.template used a BuildKit heredoc (`RUN cat <<-'EOF' >/run.sh`).
With the legacy builder it parses as `RUN cat >/run.sh` — empty stdin, 0-byte
file. Every eval container then dies with `exec /run.sh: exec format error`,
emits no events, and the run ends with Total Cost=$0 / Errors=N/N.

Replace the heredoc with a single `RUN printf … > /run.sh && chmod +x`.
Same resulting file, works on both legacy builder and BuildKit.

Author: hamza-jeddad

pkg/evaluation/Dockerfile.template

@@ -3,12 +3,7 @@
 FROM alpine:latest
 LABEL "io.docker.agent.evals.image"="default"
 COPY --from=docker/docker-agent:edge /docker-agent /
-RUN cat <<-'EOF' >/run.sh
-#!/usr/bin/env sh
-set -euo pipefail
-exec "$@"
-EOF
-RUN chmod +x /run.sh
+RUN printf '#!/usr/bin/env sh\nset -euo pipefail\nexec "$@"\n' > /run.sh && chmod +x /run.sh
 WORKDIR /working_dir
 ENV TELEMETRY_ENABLED=false
 ENV DOCKER_AGENT_HIDE_TELEMETRY_BANNER=1