fix(rlix): always resume generation after finalize

[TianyeGGBond]

What

Ensures MilesModelUpdateService._run_atomic_unit() always attempts continue_generation after the finalize_weight_update fan-out, even when finalize_weight_update raises.

Why

Before this change, the sequence was:

pause_generation(mode="retract")
await _ray_get(finalize_refs)
continue_generation()

If finalize_weight_update failed or timed out, control left _run_atomic_unit() before continue_generation() ran. Any engine paused by the pre-finalize pause_generation(mode="retract") could remain paused indefinitely, causing the next generate path to hang in a misleading way.

Correctness Semantics

This change does not treat a failed weight update as successful.

continue_generation here is only cleanup for the SGLang scheduler pause state. If finalize_weight_update fails:

• the original exception still propagates
• set_weight_version is not called
• the pipeline does not publish the failed version
• the driver/training loop still fails fast and can run cleanup

So the failure remains explicit, but we avoid leaking the engine in a paused control-plane state.

Before

finalize_refs = [h.finalize_weight_update.remote() for h in handles.values()]
await _ray_get(finalize_refs)

try:
    cont_refs = [h.continue_generation.remote() for h in handles.values()]
    await _ray_get(cont_refs)
except Exception as exc:
    logger.warning(...)

After

finalize_refs = [h.finalize_weight_update.remote() for h in handles.values()]
try:
    await _ray_get(finalize_refs)
finally:
    try:
        cont_refs = [h.continue_generation.remote() for h in handles.values()]
        await _ray_get(cont_refs)
    except Exception as exc:
        logger.warning(...)

Tests

Added a lightweight regression test that checks the cleanup contract structurally, without Ray or GPU dependencies:

python -m pytest -q tests/test_miles_model_update_service_cleanup.py

Result:

1 passed in 0.03s

Scope

Exception-safety hardening only. Happy-path ordering and version publishing behavior are unchanged.

[howard989]

lgtm