frank-dragoon: promote the A/B verification harness into the repo

The three artifacts that produced the native-vs-swift15 verdict, so the next
payload swap starts from instruments instead of ad-hoc scripts:

  census-frank-dragoon.sh — the engine's own checkpoint tools (verify/ppl/niah)
    over BOTH payloads under one knob set; the pool stays 524288 deliberately
    because the ppl pass scores 297,053 ids as two 262,144-token sequences.
  battery-frank-dragoon.py — behavior battery against the live service: refusal
    census, thinking-token census, tool-call turns, the red-PNG vision probe,
    needle-in-haystack, decode/prefill/prompt-cache rates; discards the
    post-boot warmup request and records the engine's 400 body (which names the
    exact token overage) instead of dying on it.
  trial-frank-dragoon.sh — the guarded candidate window: fetch gate, verify,
    stop+mask, census, boot through a transient FRANK_DRAGOON_ENV_FILE drop-in,
    battery, trap-guarded restore.

scripts/trial-frank-dragoon.sh

@@ -0,0 +1,57 @@
+#!/usr/bin/env bash
+# swap.sh — run frank-dragoon on the candidate env through a transient systemd
+# drop-in (the fleet's A/B law: restart the SERVICE with a different
+# FRANK_DRAGOON_ENV_FILE, never a scratch port — one iGPU holds one server).
+#
+#   swap.sh candidate   install the drop-in, restart, print the boot ledger
+#   swap.sh restore     retire the drop-in (moved, never deleted), restart back
+#                       onto the repo env, print the boot ledger
+set -euo pipefail
+
+UNIT=frank-dragoon
+DROP=/etc/systemd/system/$UNIT.service.d/v2abl.conf
+ENVF=/tmp/frank-dragoon-v2abl.env
+LOG=/home/dank/logs/frank_dragoon.log
+
+ledger() {
+    echo "--- boot ledger (kv pool / weights / mtp / clamp)"
+    grep -aiE "kv pool|KV budget|checkpoint:|n-gram|vision|pinned|memory:|clamp|warn|error|MTP|prompt cache|version" \
+        "$LOG" | head -30
+}
+
+case "${1:-}" in
+  candidate)
+    [ -f "$ENVF" ] || { echo "missing $ENVF" >&2; exit 1; }
+    sudo mkdir -p "$(dirname "$DROP")"
+    printf '[Service]\nEnvironment=FRANK_DRAGOON_ENV_FILE=%s\n' "$ENVF" \
+        | sudo tee "$DROP" >/dev/null
+    sudo systemctl daemon-reload
+    # the census window masks the unit; a masked unit cannot be started
+    sudo systemctl unmask "$UNIT" 2>/dev/null || true
+    sudo systemctl restart "$UNIT"
+    echo "--- waiting for the listener (load is minutes; the listener opens after the full load)"
+    for _ in $(seq 1 120); do
+        curl -sf -m 5 -o /dev/null "http://127.0.0.1:7770/health" && break
+        sleep 5
+    done
+    systemctl is-active "$UNIT"
+    curl -s -m 5 http://127.0.0.1:7770/v1/models | head -c 300; echo
+    ledger
+    ;;
+  restore)
+    if [ -f "$DROP" ]; then
+        sudo mv "$DROP" "/tmp/v2abl.conf.retired-$(date +%s)"
+        sudo systemctl daemon-reload
+    fi
+    sudo systemctl unmask "$UNIT" 2>/dev/null || true
+    sudo systemctl restart "$UNIT"
+    for _ in $(seq 1 120); do
+        curl -sf -m 5 -o /dev/null "http://127.0.0.1:7770/health" && break
+        sleep 5
+    done
+    systemctl is-active "$UNIT"
+    curl -s -m 5 http://127.0.0.1:7770/v1/models | head -c 300; echo
+    ledger
+    ;;
+  *) echo "usage: $0 candidate|restore" >&2; exit 2 ;;
+esac