fix(mailbox-tests): the owed-set suite's own gate refused to let it run on node 24

scripts/test-owed-withdrawal.sh has not executed a single assertion since the
image moved to node 24. Its precondition line

    node --experimental-strip-types --check "$SRC"

exits 2 on an unmodified extensions/pi/mempalace.ts, and the script is
`set -euo pipefail` with `|| exit 2`, so all 17 assertions and both regression
guards were skipped. Measured on pi-devbox v1.9.1, node v24.21.0.

CAUSE, MEASURED AND NARROWER THAN IT LOOKS. The reported error names the inline
type-import at mempalace.ts:92, which invites the reading "that import is
unusual". It is not the import: `node --check` does not type-strip AT ALL. A file
whose entire content is `const x: number = 1;` fails identically, with or without
--experimental-strip-types, while `node --experimental-strip-types <same file>`
executes it fine. --check has never been type-aware; execution is what gained
stripping. So this gate could never validate TypeScript, on any node.

WHY IT USED TO PASS -- INFERENCE, NOT MEASUREMENT. e2b060a's message records this
suite running on 2026-09-09 with a control pass and four mutation kills, when the
image shipped node v22.23.2; v1.9.1 ships v24.21.0. No node 22 exists on the box
where this was diagnosed, so the counterfactual was not executed. Treat "22
stripped for --check and 24 stopped" as a hypothesis consistent with the record,
not as a measured cause. What IS measured is the present-tense behaviour above.

WHY THIS MATTERS MORE THAN A RED TEST. This suite exists because isWithdrawn is
the one rule in the extension that can go wrong SILENTLY -- a wrong rule does not
throw and does not log, it makes a real unanswered ask vanish from a mailbox
forever. The rule shipped in e2b060a and has been baked since v1.9.1; the thing
that makes its failure mode visible has been dark for the same period. The
mitigating half: it failed CLOSED (exit 2, loud), never vacuously green. A gate
that cannot run must not pass, and it did not.

THE FIX. Strip first, then syntax-check the emitted JS: version-stable, and it
still refuses malformed input. `mode: "strip"` blanks type syntax without moving
anything, so offsets and line numbers survive and a reported error line still
points at the right line of the original .ts (69157 B in, 69157 B out).

THE EXIT CODES ARE NOW SPLIT, AND THAT IS THE POINT. 3 = the gate itself cannot
run (no module.stripTypeScriptTypes, i.e. node < 22.13). 2 = the source does not
parse. Collapsing the two is how this defect disguised itself: it printed
"mempalace.ts does not parse" while mempalace.ts was fine, sending a reader to
inspect the wrong file. Note the stripper is itself a parser, so a genuine syntax
error surfaces as an exception from the strip call rather than from --check; that
path is caught and reported as 2, not 3. Both remain failures. Neither passes.

VERIFIED IN SIX DIRECTIONS on this image, each expectation written down first:
  unmutated source          -> rc=0, PASSED (17/17)
  malformed TypeScript      -> rc=2, "does not parse: Expression expected"
  stripper made unavailable -> rc=3, "cannot strip", and NOT "does not parse"
                               (simulated by doctoring the runtime through
                               NODE_OPTIONS, so the shipped line ran as shipped)
  M1 marker requirement removed -> FAILED: 3   (no-marker, other-thread, prose)
  M2 third-party guard removed  -> FAILED: 1
  M3 to_agent guard removed     -> FAILED: 2   (broadcast and wrong-device share it)
  M4 ordering guard removed     -> FAILED: 1
The four kill counts are the same ones e2b060a recorded, so sensitivity is
restored rather than merely asserted.

WORTH KNOWING FOR THE NEXT PERSON WHO MUTATES THIS: the extractor carries its own
guard that rejects an isWithdrawn which no longer mentions "withdraws", so the
obvious M1 (delete the marker check outright) is refused before any assertion
runs -- correctly, but it looks like a crash. Mutate to `... || true` instead,
which removes the requirement while keeping the key mentioned.

SC2016 is disabled on the node invocation with a stated reason: the single quotes
are deliberate, the payload is JavaScript and `${process.version}` must reach
node rather than the shell. Checked that the file is shellcheck-clean at default
severity, as it was before this change, and at the -S error severity the
pi-devbox gate uses.

NOT FIXED HERE. Nothing in CI runs this suite -- it is a script an operator
invokes, which is precisely why a gate that fails loudly still went unnoticed
across a node bump. The harness's own runner two hundred lines below still passes
--experimental-strip-types, deliberately: it is a no-op on 24 and required on 22,
so it keeps the suite runnable on both. And the real reason this was found at all
is unrelated to CI: isWithdrawn was being exercised end-to-end on a released
image against the live logstream for the first time (project/pi-devbox seq 140),
and the suite was reached for as corroboration.

scripts/test-owed-withdrawal.sh

@@ -23,7 +23,9 @@
 # withdrawal had no effect, so tor-ms22 was still being told it owed a reply 41h
 # later for a release it never installed.
 #
-# Usage: scripts/test-owed-withdrawal.sh [source.ts]   (exit 0 = all rules behave)
+# Usage: scripts/test-owed-withdrawal.sh [source.ts]
+#   exit 0 = all rules behave   1 = a rule broke
+#   exit 2 = source unreadable or does not parse   3 = the gate itself cannot run
 #
 # The optional argument exists so the suite can be pointed at a deliberately
 # MUTATED copy of the source to prove it is sensitive — a suite that has never
@@ -39,8 +41,47 @@ trap 'rm -rf "$WORK"' EXIT
 [ -r "$SRC" ] || { echo "FAIL: cannot read $SRC" >&2; exit 2; }
 
 # A gate that cannot run must not pass — the standing rule in this repo.
-node --experimental-strip-types --check "$SRC" \
+#
-  || { echo "FAIL: $SRC does not parse" >&2; exit 2; }
+# NOT `node --check`: it does not type-strip, so it rejects ANY TypeScript —
+# `const x: number = 1` included, not just the inline type-import at the top of
+# mempalace.ts. It passed on node 22.x and stopped passing on node 24.x
+# (measured on pi-devbox v1.9.1, node v24.21.0: this gate exited 2 on an
+# unmodified mempalace.ts, so all 17 assertions below refused to run). Strip
+# first, then syntax-check the emitted JS. `mode: "strip"` blanks type syntax
+# without moving anything, so byte offsets and line numbers survive and a
+# reported error line still points at the right line of the ORIGINAL .ts.
+#
+# The two failure modes are reported separately and on purpose. "Cannot strip"
+# is a fact about the toolchain; "does not parse" is a fact about the source.
+# Collapsing them is what made this very defect present itself as
+# "mempalace.ts does not parse" when mempalace.ts was fine.
+#
+# SC2016 is disabled deliberately: the single quotes are the point. What follows
+# is JavaScript, and `${process.version}` must reach node, not be expanded by the
+# shell first.
+# shellcheck disable=SC2016
+node --no-warnings -e '
+  const { readFileSync, writeFileSync } = require("node:fs");
+  const { stripTypeScriptTypes } = require("node:module");
+  if (typeof stripTypeScriptTypes !== "function") {
+    console.error(`FAIL: node ${process.version} cannot strip TypeScript ` +
+      `(module.stripTypeScriptTypes needs >= 22.13) — the gate is unavailable, ` +
+      `which is NOT a statement about the source`);
+    process.exit(3);
+  }
+  let js;
+  try {
+    js = stripTypeScriptTypes(readFileSync(process.argv[1], "utf8"), { mode: "strip" });
+  } catch (err) {
+    // The stripper is itself a parser, so a syntax error lands HERE, not in the
+    // --check below. This is a statement about the source: exit 2, not 3.
+    console.error(`FAIL: ${process.argv[1]} does not parse: ${err.message}`);
+    process.exit(2);
+  }
+  writeFileSync(process.argv[2], js);
+' "$SRC" "$WORK/stripped.mjs" || exit $?
+node --check "$WORK/stripped.mjs" \
+  || { echo "FAIL: $SRC does not parse (stripped output rejected)" >&2; exit 2; }
 
 # ---------------------------------------------------------------- extractor ---
 cat >"$WORK/extract.mjs" <<'EXTRACT'