test(ci): temporary probe — is the lyrical interop failure present on unmodified main?

[YuanYuYuan]

Temporary. Do not merge. This PR will be closed as soon as the interop matrix reports.

Why it exists

Interop tests with ROS 2 lyrical fails on #301 across four runs, always the same way:

test_hiroz_add_two_ints_server_to_rcl_client ... FAILED
demo_nodes.rs: RCL add_two_ints client exited with failure status ExitStatus(unix_wait_status(64000))

The failing assertion is that a prebuilt C++ client from the distro image exits 250 while
talking to a hiroz server whose source is byte-identical to main. #301 does not touch
service.rs, hiroz-protocol, the test harness or test.yml, and reverting the one example
change did not affect the result.

main last ran the interop matrix on 2026-08-06. The job pulls ros:lyrical-ros-base, a tag
that is rebuilt as packages update, so "green on main" describes a six-day-old image rather
than today's.

What this measures

This branch is main plus a single comment line, which is the smallest change that still
triggers the workflow — **.md is in paths-ignore, and draft PRs are skipped.

lyrical result here	conclusion
fails	the image drifted; #301 is not the cause
passes	something in #301 is responsible after all, and the search continues

Either answer is worth having. The alternative was asserting "not our fault" without evidence.

[YuanYuYuan]

Closing: the lyrical failure is already being fixed elsewhere, so this probe is not needed. Nothing here was intended to merge.