feat(dynamo): add native inference backend

[biswapanda]

Summary

Adds Dynamo as a first-class Prime RL inference provider and routes rollout generation through the provider-neutral generate request/response path.

This branch is rebased directly on canonical Prime RL main at 84b413fd73a5b5f85f772e42bf1beb52fe0a265e; the current PR head is f077fbf9620f144ec2cd5d74c4dc0eb147f5ceb2.

What changed

• adds Dynamo provider configuration, launch, discovery, and admin integration;
• carries policy-version metadata through generation for strict off-policy control;
• coordinates pause/resume and distributed NCCL weight updates across discovered workers;
• unifies generation behind the common request/response model;
• updates policy-marker handling for the current verifiers TraceTask API;
• expands focused configuration, barrier, and inference tests.

Why it is needed

Prime RL previously assumed direct ownership of native vLLM workers. Dynamo introduces a frontend/router and independently discovered prefill/decode workers, so rollout traffic and administrative weight-update traffic must be separated while retaining stable worker identity, policy-version accounting, and synchronized weight publication.

Validation

• 17/17 orchestrator/barrier tests passed;
• 11/11 Dynamo configuration tests passed;
• 181/181 stacked Prime inference/Kubernetes tests passed;
• a broader targeted run passed 304 tests; 17 collection cases were unavailable only because optional external task-set plugins were not installed;
• controlled Qwen3-30B-A3B-Thinking-2507 Hendrycks Math E2E passed in native-Dynamo and OpenEngine modes using the same digest-pinned image:
  • five orchestrator and five four-rank trainer steps in each mode;
  • maximum off-policy distance remained 0 for every step;
  • all four workers reached final weight version 3;
  • post-training generation returned 16 tokens in each mode;
  • trainer/GPU cleanup, release deletion, and artifact-manifest verification passed.

Accepted evidence:

• baseline: /data/openengine-e2e/runs/q30-baseline-final-20260711T111946Z
• OpenEngine: /data/openengine-e2e/runs/q30-openengine-final-20260711T114759Z
• image digest: sha256:9c0f57ca6634a569e1df53089cecf6f5d6b622e9e49bb58ebc609f976157e1e6

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit b653a77. Configure here.}