Add Nanbeige4.2-3B export support

[micwill755]

Summary

Adds TensorRT Edge Exporter support for Nanbeige/Nanbeige4.2-3B.

Nanbeige uses a looped-transformer architecture with 22 physical decoder layers executed twice. This change:

• Registers a Nanbeige EdgeSpec.
• Implements loop-aware language export with 44 logical KV-cache slots.
• Adds live class patching for the trust_remote_code model.
• Uses the TensorRT attention plugin with causal attention.
• Repairs invalid deterministic RoPE buffers caused by Transformers remote-code version drift.
• Adds an end-to-end Nanbeige export example.
• Moves the live GR00T patch context into its family spec and aligns the PI05 example loader naming.

Motivation and context

Nanbeige4.2-3B reuses the same transformer blocks across multiple loops while requiring independent KV-cache state for each logical layer execution. Existing causal-LM export paths only process each physical layer once and therefore cannot represent this architecture correctly.

The model's remote code also targets an older Transformers version. With the current environment, its non-persistent RoPE frequency buffers may be zero-filled or invalid after loading. The compatibility helper deterministically reconstructs those buffers from the model configuration before eager parity capture.

Validation

Tested end-to-end with Nanbeige/Nanbeige4.2-3B in FP16:

• Eager/TRT mean absolute error: 0.008464
• Maximum absolute error: 0.046875
• Relative L2 error: 0.0016
• Values within tolerance: 99.4%
• Eager execution: 15.948 ms
• TensorRT execution: 9.446 ms
• Speedup: 1.688x

Targeted Edge Exporter unit tests and pre-commit formatting/lint hooks pass locally.

Dependencies

• Stacked on Always compile Edge engines and dual-profile PI05 language I/O #4691.
• Uses the existing Edge Exporter TensorRT attention plugin.
• Requires Hugging Face remote code for Nanbeige/Nanbeige4.2-3B.
• No new package dependencies are introduced.

Type of change

• New feature (non-breaking change which adds functionality)

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented hard-to-understand compatibility and patching behavior
• I have added the relevant labels so that relevant reviewers are notified