fix(runner): release the file teardown when stop-on-failure halts

[Chemaclass]

🤔 Background

Related #1321

--stop-on-failure ends a sequential run with exit from inside the test loop, so the loop's own tear_down_after_script call is never reached. Whatever set_up_before_script acquired is leaked, and nothing in the output says the hook was skipped.

💡 Changes

• Track the file whose teardown this shell still owes, and settle it from the exit path, before the summary and before the temp dirs a hook may still be reading.
• Gate the debt on the file declaring the hook. With none declared the hook call prints a blank line, and emitting that from the halt path would change the output of every halted run.
• Turning the exit into a loop flag was the other option. It reroutes the halt through a path guarded by parallel::is_enabled, so it would rewrite all five stop-on-failure snapshots and start writing reports sequentially. Neither belongs in this fix.
• All five existing snapshots stay byte-identical.