feat(hygon): enable modern Infini stack inference

[gongchensu]

Summary

• Register Hygon with the canonical InfiniOps device bridge, RoPE, greedy sampling, and FlashAttention prefill/decode adapters.
• Extend scripts/build_infini_stack.py to build the Hygon gfx936 stack with standalone InfiniRT, linked InfiniOps providers, and RCCL-enabled InfiniCCL.
• Require the Hygon InfiniOps operator selection through an external --operator-config, consistent with the Iluvatar integration workflow.
• Add focused build-command and runtime-contract coverage for the Hygon path.

Motivation

The modern Infini stack did not previously expose a complete Hygon inference path in InfiniLM. Hygon devices were rejected by the model runner and FlashAttention validation, and the canonical InfiniOps bridge and attention dispatchers did not register Hygon.

This change enables Hygon inference through canonical InfiniOps operators and standalone InfiniRT, including linked FlashAttention providers and RCCL-based tensor parallelism. Platform-specific operator selection remains external to the repository, following the review decision established for Iluvatar.

Type of Change

• feat — new feature / new model
• fix — bug fix
• perf — performance improvement (no behavioral change)
• refactor — code restructuring without behavior change
• test — adding or fixing tests only
• docs — documentation only
• build / ci — build system or CI configuration
• chore — tooling, formatting, or other non-code changes
• Breaking change

Test Results of Involved Models on Supported Platforms (Please attach screenshots)

Benchmark / Performance Impact

Notes for Reviewers

CI / ChatOps

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