Add durable server-owned inference commands

[akgohain]

Summary

Moves approved agent inference requests onto the same durable server-command pattern already used for training.

• Approval now stages a queued start_inference workflow command.
• The server resolves workflow paths/configuration, submits inference idempotently, and records a workflow operation plus inference events.
• The client monitors the accepted command without launching inference a second time in the browser.
• Existing manual inference launch behavior remains unchanged.

Follow-on

This layer records successful worker acceptance. A later stacked PR will reconcile true worker completion, failure, cancellation, and recovery into durable operation state.

Verification

• uv run pytest -q tests/test_pytc_runtime_routes.py tests/test_workflow_routes.py — 107 passed
• Focused frontend tests — 20 passed
• Production frontend build passed (pre-existing EHTool hook warnings remain).