feat: unify jobs + mmt under jobs command

[tejapulagam]

Summary

• Route multi-machine training through lightning job so one CLI covers single- and multi-machine jobs.
• job run --num-machines N (default 1) creates an MMT when N > 1.
• job list includes both Jobs and MMTs (num_machines column).
• job inspect / logs / ssh accept --rank for MMT workers.
• job stop / delete resolve Job or MMT and act on the whole resource (no per-rank stop/delete).
• Shared resolution helpers in resource_resolution (resolve_job_or_mmt, resolve_mmt_machine).
• lightning mmt left in place for now (deprecation later).

Test plan

• job run with default --num-machines 1 still creates a Job
• job run --num-machines 2 creates an MMT
• job list shows Jobs and MMTs with correct num_machines
• job inspect / logs / ssh work for Jobs; with --rank for MMT workers
• job stop / delete stop/delete an entire MMT (not a single rank)
• Existing lightning mmt commands still work
• Unit tests: python/tests/cli/job/ + test_resource_resolution.py

[justusschock]

This should match with the SDK though, so we'd need to merge both classes as well (which would be doable).