refact(frank-dragoon): serve gates run on the shared gate library

The hand-written image/ck/tokenizer gates are require_image, require_bytes and
require_dir_files from scripts/lib/llm-gates.sh. The serve seam is unchanged
and still green (its podman stub now models `podman image exists`, the
primitive the gate uses). Behaviour preserved: every refusal names the
artifact, the endpoint and the fetch script.

scripts/lib/llm-gates.sh

@@ -69,12 +69,14 @@ require_min_mib() {
 
 # require_dir_files — DIR must be a directory and every named member a
 # regular file (the flat-tokenizer law: snapshot symlinks dangle in the
-# container mount even when the directory itself is real).
+# container mount even when the directory itself is real. A symlinked
+# DIRECTORY is refused too: a HF cache snapshot can link the directory
+# itself, and a link dangles inside the container mount.
 require_dir_files() {
     local dir="$1" label="$2" hint="$3"
     shift 3
     local f
-    if [[ ! -d "$dir" ]]; then
+    if [[ -L "$dir" || ! -d "$dir" ]]; then
         _gate_fail "$label: missing at $dir" "$hint"
     fi
     for f in "$@"; do

scripts/serve-frank-dragoon.sh

@@ -29,7 +29,14 @@
 # exactly like frank-archon's.
 set -euo pipefail
 
+# The artifact gates are the shared library — the serve script and the
+# deployer refuse the same missing/truncated payload with the same words
+# (the 2026-10-01 crash-loop was the two hand-written twins disagreeing).
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+export GATE_PREFIX=frank-dragoon
+# shellcheck disable=SC1091
+source "$SCRIPT_DIR/lib/llm-gates.sh"
+
 ENV_FILE="${FRANK_DRAGOON_ENV_FILE:-$SCRIPT_DIR/frank-dragoon.env}"
 if [ ! -f "$ENV_FILE" ]; then
     echo "frank-dragoon: env file not found: $ENV_FILE" >&2
@@ -57,55 +64,37 @@ set +a
 : "${HALOGEN_KV_SLOTS:?HALOGEN_KV_SLOTS must be set}"
 : "${HALOGEN_SPEC_ADAPT:?HALOGEN_SPEC_ADAPT must be set (0 = head always on)}"
 
-# Capture podman's output BEFORE grepping: under `set -o pipefail` the
-# `podman images | grep -q` pattern races (grep exits on first match,
-# podman dies SIGPIPE 141, pipefail turns the 141 into "no match" — the
-# 2026-09-30 deploy refusal).
-DIGESTS="$(podman images --format '{{.RepoDigests}}')"
-if ! grep -qF "${FRANK_DRAGOON_IMAGE#*@}" <<<"$DIGESTS"; then
-    echo "frank-dragoon: image $FRANK_DRAGOON_IMAGE not in podman storage;" >&2
-    echo "  pull it: podman pull ${FRANK_DRAGOON_IMAGE%@*}" >&2
-    exit 1
-fi
+# The image gate is the digest-pinned ref itself: `podman image exists` takes
+# a name@sha256 ref in one command, so a retagged look-alike or a newer
+# latest cannot satisfy it and there is no pipefail/SIGPIPE race with grep
+# (the 2026-09-30 deploy refusal). Runs as dank: the unit's process uses
+# dank's rootless storage.
+require_image "$FRANK_DRAGOON_IMAGE" \
+    "pull it: podman pull docker://$FRANK_DRAGOON_IMAGE" || exit 1
 
 # Size-exact gates on all three payload files: a truncated curl exits 0 on
 # some failures and a partial .hgn loads far enough to look alive, so the
 # byte counts from the Hub tree API are the contract (fleet fetch law).
-ck() {
-    # ck <env-name> <path> <expected-bytes>
-    if [ ! -f "$2" ]; then
-        echo "frank-dragoon: $1 $2 missing;" >&2
-        echo "  fetch it: bash scripts/download-frank-dragoon-flashnext.sh" >&2
-        exit 1
-    fi
-    local sz
-    sz="$(stat -c %s "$2")"
-    if [ "$sz" != "$3" ]; then
-        echo "frank-dragoon: $1 is $sz bytes, expected $3 (partial download?)" >&2
-        exit 1
-    fi
-}
-ck checkpoint "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_CHECKPOINT" "$FRANK_DRAGOON_CHECKPOINT_BYTES"
-ck n-gram-table "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_NGRAM_TABLE" "$FRANK_DRAGOON_NGRAM_BYTES"
-ck vision-tower "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_VISION_TOWER" "$FRANK_DRAGOON_VISION_BYTES"
+require_bytes "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_CHECKPOINT" \
+    checkpoint "$FRANK_DRAGOON_CHECKPOINT_BYTES" \
+    "fetch it: bash scripts/download-frank-dragoon-flashnext.sh" || exit 1
+require_bytes "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_NGRAM_TABLE" \
+    n-gram-table "$FRANK_DRAGOON_NGRAM_BYTES" \
+    "fetch it: bash scripts/download-frank-dragoon-flashnext.sh" || exit 1
+require_bytes "$FRANK_DRAGOON_MODEL_DIR/$FRANK_DRAGOON_VISION_TOWER" \
+    vision-tower "$FRANK_DRAGOON_VISION_BYTES" \
+    "fetch it: bash scripts/download-frank-dragoon-flashnext.sh" || exit 1
 
 # The payload ships the tokenizer as a FLAT DIRECTORY. A HuggingFace cache
 # snapshot symlinks each file into a sibling blobs/, and those symlinks
 # dangle inside the container mount — so the directory must be real and
 # every named file must be a regular file, not a link.
-TOK_DIR="$FRANK_DRAGOON_MODEL_DIR/tokenizer"
-if [ -L "$TOK_DIR" ] || [ ! -d "$TOK_DIR" ]; then
-    echo "frank-dragoon: tokenizer dir $TOK_DIR missing or a symlink (HF cache snapshot?);" >&2
-    echo "  fetch it: bash scripts/download-frank-dragoon-flashnext.sh" >&2
-    exit 1
-fi
-for TF in $FRANK_DRAGOON_TOKENIZER_FILES; do
-    if [ ! -f "$TOK_DIR/$TF" ] || [ -L "$TOK_DIR/$TF" ]; then
-        echo "frank-dragoon: tokenizer file $TOK_DIR/$TF missing or a symlink;" >&2
-        echo "  fetch it: bash scripts/download-frank-dragoon-flashnext.sh" >&2
-        exit 1
-    fi
-done
+# The tokenizer file list is word-separated ON PURPOSE (one argument per
+# file), so the unquoted expansion below is the interface, not a slip.
+# shellcheck disable=SC2086
+require_dir_files "$FRANK_DRAGOON_MODEL_DIR/tokenizer" tokenizer \
+    "fetch it: bash scripts/download-frank-dragoon-flashnext.sh" \
+    $FRANK_DRAGOON_TOKENIZER_FILES || exit 1
 
 # GPU access is mandatory but the node paths are variables so the seam can
 # drive the gate on a box without an AMD GPU.
@@ -115,6 +104,7 @@ if [ ! -e "$DEV_KFD" ] || [ ! -d "$DEV_DRI" ]; then
     echo "frank-dragoon: $DEV_KFD or $DEV_DRI missing — no gfx1151 to serve on" >&2
     exit 1
 fi
+
 # Host-RAM preflight — the engine's pin gate, checked BEFORE podman run.
 # The engine refuses to pin when MemAvailable is below the checkpoint plus
 # a 16 GiB floor: pinned pages cannot be swapped, and under the floor the