test_util_format_with_options: formatWithOptions returns undefined instead of delegating to util.format

[proggeramlug]

Symptom

test-files/test_util_format_with_options.ts is failing the parity gate
on every PR rebased onto current main (seen blocking #944, #947, #951,
#953, #956, #957, #958 — and now also #947 again after rebase). It has
been the sole entry in NEW FAILURES (not in known_failures.json) for
each of those runs since #952, after #958 cleared the
crypto.subtle.encrypt failure that was masking it.

Reproduction

cargo build --release -p perry-runtime -p perry-stdlib -p perry
PERRY_ALLOW_UNIMPLEMENTED=1 ./target/release/perry \
  test-files/test_util_format_with_options.ts -o /tmp/p
node --experimental-strip-types test-files/test_util_format_with_options.ts
/tmp/p

node (expected)

Hello world
x=k y=7

perry (actual)

undefined
undefined

Diagnosis pointer

util.formatWithOptions was added in #948 (b384b942 feat(util): add util.formatWithOptions (v0.5.970)). The PR description says:

The JS stub ignores the inspect-options bag and delegates to the
existing util.format — full options-passthrough is a follow-up.

The delegation isn't happening at runtime: every call returns
undefined. The HIR/manifest gate is being lifted correctly (no
compile error, no R005), but the runtime stub either isn't routed or
returns the wrong thing.

Likely suspects:

• The formatWithOptions stub in crates/perry-stdlib doesn't
  actually invoke util.format (or returns before the call).
• The function is registered but the dispatch tag returns
  undefined for the no-options-touching first-arg case.

test-files/fixtures/util_format_with_options/ may have additional
context if it exists.

Why fix this now

The parity gate's NEW-FAILURES check is exit 1 on a single uncategorized
new failure. With this regression undiagnosed, every PR maintainer has to
either admin-bypass or add the test to known_failures.json (which would
hide the real bug). Admin-bypass was already used to land #958 today.

Acceptance

• formatWithOptions({}, "Hello %s", "world") returns "Hello world" at runtime.
• formatWithOptions({ colors: false }, "x=%s y=%d", "k", 7) returns "x=k y=7".
• test_util_format_with_options passes the parity comparison against node --experimental-strip-types.
• No new entries in test-parity/known_failures.json (i.e. the fix lands, not a skip).