phase-20.45: MirBuilder-prefer match canary

- Add mirbuilder_prefer_mirbuilder_match_core_exec_canary_vm.sh (Expect rc=42)

tools/smokes/v2/profiles/quick/core/phase2043/mirbuilder_prefer_mirbuilder_match_core_exec_canary_vm.sh

@@ -0,0 +1,27 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"; if ROOT_GIT=$(git -C "$SCRIPT_DIR" rev-parse --show-toplevel 2>/dev/null); then ROOT="$ROOT_GIT"; else ROOT="$(cd "$SCRIPT_DIR/../../../../../../../../.." && pwd)"; fi
+source "$ROOT/tools/smokes/v2/lib/test_runner.sh"; require_env || exit 2
+
+tmp_prog="/tmp/prog_prefer_mirbuilder_match_$$.json"
+cat >"$tmp_prog" <<'JSON'
+{"version":0,"kind":"Program","body":[
+  {"type":"Return","expr":{"type":"Match","scrutinee":{"type":"Str","value":"A"},
+   "arms":[{"label":"A","expr":{"type":"Int","value":42}}, {"label":"B","expr":{"type":"Int","value":0}}],
+   "else":{"type":"Int","value":1}}}
+]}
+JSON
+
+set +e
+HAKO_PREFER_MIRBUILDER=1 HAKO_VERIFY_PRIMARY=core verify_program_via_builder_to_core "$tmp_prog" >/dev/null 2>&1
+rc=$?
+set -e
+rm -f "$tmp_prog" || true
+
+if [ "$rc" -eq 42 ]; then
+  echo "[PASS] mirbuilder_prefer_mirbuilder_match_core_exec_canary_vm"
+  exit 0
+fi
+echo "[FAIL] mirbuilder_prefer_mirbuilder_match_core_exec_canary_vm (rc=$rc, expect 42)" >&2; exit 1
+