fix(release): fail smoke test on SIGKILLed binary

The release smoke test only treated exit 126 and 127 as exec failures,
so a compiled macOS binary killed by the kernel for an invalid code
signature (exit 137) passed silently and would have shipped dead on
arrival. Treat 137 as a fatal smoke failure.

Author: brianjfox

scripts/release.sh

@@ -176,7 +176,9 @@ smoke_bin() {  # smoke_bin LABEL BINARY
   local rc=0
   "$bin" --__release_smoke__ >/dev/null 2>&1 || rc=$?
   # 126 = cannot execute, 127 = not found — real link/exec failures.
-  if [ "$rc" -eq 126 ] || [ "$rc" -eq 127 ]; then
+  # 137 = SIGKILL before any code ran: on macOS that is the kernel rejecting an
+  # invalid code signature (see compile_bin), so the binary is dead on arrival.
+  if [ "$rc" -eq 126 ] || [ "$rc" -eq 127 ] || [ "$rc" -eq 137 ]; then
     die "smoke: cannot execute $label binary (rc=$rc)"
   fi
   # Non-zero from "unrecognized flag" (or similar) still proves the binary ran.