feat: Job metadata is also registered as labels

[TrevorBasinger]

Summary

This PR adds additive, reserved job system labels under roar.*, derived from existing local job metadata while keeping jobs.metadata intact
for downstream compatibility.

What changed

• derive roar.* system labels for local jobs from existing metadata
• refresh those labels on job creation/update paths, including:
  • local run/get/put jobs
  • OSMO host execution updates
  • Ray/OSMO fragment reconstitution
  • post-reconstitution composite materialization
• reserve roar.* from manual label set/copy operations
• hide roar.* from default show/DAG rendering to avoid noisy user-facing output
• sync current job system labels to GLaaS, including publish-time put jobs
• update unit/integration/live label expectations accordingly

Notes

• existing metadata blobs are preserved unchanged
• existing artifact system labels under dataset.* are unchanged
• this is an additive migration step toward label-backed job metadata

Testing

• ruff check .
• mypy roar
• pytest -m "not live_glaas and not ebpf" -q

[christophergeyer]

🚢 it.