rollout: subtract agent-reported tool time from throughput accounting

[Shi-Dong]

Summary

Adds a small, env-agnostic hook to the generic agentic generate function (miles/rollout/generate_hub/agentic_tool_call.py) so that wall-clock time an agent spends outside policy generation (environment steps, tool calls, sandbox exec/eval) is surfaced on Sample.non_generation_time.

Why

agentic_tool_call.generate is the shared generate function used by every agent-environment RL path (Harbor/swe-agent-v2 and OpenEnv alike). The throughput/perf metrics in miles/ray/rollout/metrics.py derive per-sample tokens/sec from the total rollout wall-clock. In a multi-turn agentic rollout a large fraction of that wall-clock is env/tool latency, not decoding — so the reported tokens/sec is badly understated and not comparable across envs with different tool latencies. This hook lets the perf accounting subtract non-generation time and report a generation-only throughput.

How

If the agent function returns agent_metrics.total_tool_time, that value is written to non_generation_time on every turn-sample of the episode. The value must be identical across turn-samples because merge_samples collapses them with _merge_equal_value, which asserts equality. Agent functions that don't report the metric are unaffected (non_generation_time stays at its 0.0 default).

Notes

This was the only core-miles change previously bundled in #1487 (the OpenEnv tbench2 example). It is peeled out here as a standalone, generic change; #1487 now stacks on top of this branch.

[gemini-code-assist]

Code Review

This pull request adds logic to extract total_tool_time from the agent's metadata and assign it to each sample's non_generation_time attribute to account for non-generation time in throughput calculations. The review feedback suggests defensively verifying that agent_metrics is a dictionary before calling .get() and validating that total_tool_time is a non-negative number to prevent runtime errors.

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