feat: [AMD Support via SemiAnalysis][3/4] ATOM and AToMesh support

[cquil11]

Summary

Add native ROCm ATOM workers and the official AToMesh router for aggregate and prefill/decode deployments, using srt-slurm's existing endpoint allocation, Slurm launch, and health/lifecycle machinery.

• Launch atom.entrypoints.openai_server with native CLI spelling, model identity, and role-aware Mooncake transfer configuration.
• Launch atomesh with the ATOM backend, static worker topology, and worker readiness gating. Infera is not part of this layer.
• Restrict managed ATOM logical endpoints to one Slurm node each; P/D deployments can use multiple nodes and endpoints.

Unrelated fixes were extracted into standalone PRs outside this stack: vLLM hybrid-DP routing #496 and SGLang interface selection #497.

Review the stack

The upstream PRs target NVIDIA main and are manually stacked, so later upstream diffs include preceding layers. The downstream fork PRs form an actual branch-based stack (main → #1 → #11 → #7 → #14); each fork PR's Files changed tab isolates its layer for easier review.

• AMD hardware and cluster runtime: upstream #431 ↔ fork #1.
• vLLM/MoRI: upstream #432 ↔ fork #11.
• ATOM/AToMesh: upstream #433 ↔ fork #7.
• Optional observation and diagnostics: upstream #476 ↔ fork #14.

Merge in that order, then rebase the remaining layers. ATOM uses Mooncake, not MoRI; its stack position is review ordering, not an engine dependency. The core runtime does not require the observation layer, but the InferenceX launcher uses its srtctl wait command.

E2E validation is maintained only in the base PR: upstream #431 / fork #1.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 92.61745% with 11 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@7f0d2f0). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
src/srtctl/backends/atom.py	89.32%	11 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #433   +/-   ##
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  Coverage        ?   82.19%           
=======================================
  Files           ?      141           
  Lines           ?    20828           
  Branches        ?        0           
=======================================
  Hits            ?    17119           
  Misses          ?     3709           
  Partials        ?        0           

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