Unit files are now named systab_<6-char-hex> (e.g., systab_a1b2c3),
so the ID is derived from the filename — no more SYSTAB_ID comments
in unit files, no id-to-jobname mappings in edit mode. Removes
generate_job_name, get_job_id, get_job_by_id, ensure_job_id.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
