frank-primary: fix the SIGPIPE race in both image-digest gates

The classic 'podman images | grep -q' pattern races under set -o pipefail:
grep exits on its first match, podman dies SIGPIPE (141) writing the
remaining RepoDigests lines, and pipefail promotes 141 to the pipeline
status — the gate reads 'no match' and refuses to deploy (2026-09-30,
dankserver). Same bug in the serve script (it would restart-loop the
same way). Fix: capture podman's output into a variable first, grep the
variable. Patched in the R9V September deploys by luck of timing.

scripts/serve-frank-primary.sh

@@ -46,11 +46,12 @@ set +a
 : "${FRANK_PRIMARY_SEQS:?FRANK_PRIMARY_SEQS must be set}"
 : "${FRANK_PRIMARY_KV_BYTES:?FRANK_PRIMARY_KV_BYTES must be set (PER RANK)}"
 : "${FRANK_PRIMARY_KV_DTYPE:?FRANK_PRIMARY_KV_DTYPE must be set (fp8 = q8/q8 KV)}"
-: "${FRANK_PRIMARY_SPEC:?FRANK_PRIMARY_SPEC must be set (0 disables)}"
-: "${FRANK_PRIMARY_UTIL:?FRANK_PRIMARY_UTIL must be set}"
-
-# --- gates: never serve a half-finished payload or a missing image -----------
-if ! podman images --format '{{.RepoDigests}}' | grep -qF "${FRANK_PRIMARY_IMAGE#*@}"; then
+# Capture podman's output BEFORE grepping: under `set -o pipefail`, the
+# classic `podman images | grep -q` pattern races — grep exits on its first
+# match, podman dies SIGPIPE (141) writing the remaining lines, and pipefail
+# turns the 141 into "no match" (the 2026-09-30 deploy refusal).
+DIGESTS="$(podman images --format '{{.RepoDigests}}')"
+if ! grep -qF "${FRANK_PRIMARY_IMAGE#*@}" <<<"$DIGESTS"; then
     echo "serve-frank-primary: pinned image absent from rootless storage: $FRANK_PRIMARY_IMAGE" >&2
     echo "  fetch it: podman pull $FRANK_PRIMARY_IMAGE" >&2
     exit 1