_run_conventions_validator awaited proc.communicate() with no timeout —
a hung subprocess (tree-sitter deadlock, huge repo) hung the
i_am_done/pr_pass gate forever and orphaned the python subprocess on
orchestrator restart. Wrap communicate() in wait_for(120s); on timeout
kill+wait the proc and fail closed (could_not_run=True → block gate
refuses the submit), matching the validator's own fail-loud philosophy.