feat(trtllm): publish Dynamo engine metrics by default

[nv-yna]

Summary

Enable TRT-LLM engine metric publication by default for workers launched through python -m dynamo.trtllm, independently of observability.enabled.

• Add backend.publish_metrics: true by default, passing the dedicated --publish-metrics flag for prefill, decode, and aggregated workers.
• Respect explicit backend.publish_events_and_metrics: false as a master opt-out of both publication flags, regardless of publish_metrics or observability.
• Distinguish omitted/null from explicit false, including schema and YAML round-trips. When the combined setting is omitted/null, preserve observability.enabled as the existing metrics-and-events superset. With both settings enabled, both positive flags are passed.
• Recognize metrics-only publication when advertising worker metrics URLs to built-in AIPerf and custom benchmarks. Preserve KVBM endpoints and explicit URL overrides.
• Show the selected flags in dry-run output and correct the warning that previously treated the combined flag as the only way to publish metrics.
• Leave native trtllm_serve, sidecar commands, and existing sidecar URL behavior unchanged.

Default behavior

Recipe	Worker publication flags
Combined setting omitted/null; observability absent or disabled	--publish-metrics
Combined setting omitted/null; observability.enabled: true	--publish-metrics --publish-events-and-metrics
Explicit backend.publish_events_and_metrics: false; any observability setting	none
Explicit backend.publish_events_and_metrics: true; any observability setting	--publish-metrics --publish-events-and-metrics

The standalone flag does not enable KV-cache events. Explicit environment settings remain under the user's control.

Compatibility

Requires a Dynamo build containing ai-dynamo/dynamo#12162 or equivalent standalone-flag support. Older builds, including v1.4.2, reject --publish-metrics.

For older workers, backend.publish_metrics: false omits only the new flag; it does not emit the also-unsupported negative flag or silently fall back to enabling KV events. Under observability, the existing combined flag can still be enabled. Explicit backend.publish_events_and_metrics: false omits both flags and suppresses ordinary Dynamo/TRT-LLM worker scrape URLs. This does not override user-supplied publication environment variables.

Metrics-only publication performs engine telemetry work; this PR does not claim zero overhead or alter the engine's profiling configuration.

Validation

• uv run pytest tests/ -q: 2109 passed, 2 skipped, 6 deselected.
• Focused worker/schema/observability/benchmark tests: 294 passed; dry-run tests: 50 passed. Includes explicit-false precedence, all worker modes, both YAML loaders, and omitted-to-null serialization followed by observability expansion.
• uv run ruff check src/srtctl/: passed.
• git diff --check: passed.
• Configured pre-commit formatting passed for the changed source and dry-run/worker/observability tests. The pinned Ruff hook reports an existing UP038 at the unchanged sidecar validation in schema.py, also present on upstream main. test_benchmarks.py retains its pre-existing 19 SIM117 findings and two formatting differences; no unrelated cleanup included.

Draft pending live validation with a compatible Dynamo runtime. No GPU jobs were launched and no existing benchmark runs or shared run artifacts were modified.

[codecov-commenter]

Codecov Report

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Additional details and impacted files

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