[CUDA] Add compact GatedDeltaNet operator (#32282)
### Description
- Add the CUDA `GatedDeltaNet` contrib operator with recurrent decode
and tensor-core chunked prefill paths.
- Support ragged and rank-4 inputs, fused Qwen gate normalization, and
native GDN arithmetic from raw `A_log`.
- Return the compact three-output ABI `[output, final_state,
state_update]`. The FP32 `state_update` capsule packs decay, shared-key,
and delta transitions needed to replay accepted speculative prefixes
without materializing dense recurrent checkpoints.
- Add schema and shape validation, CUDA registration, focused tests, a
microbenchmark, and an authored operator guide.
### Motivation and Context
Dense recurrent checkpoints scale the full FP32 state with draft width.
At the Qwen3.8 geometry, a four-slot window across 48 GDN layers
consumes 576 MiB. Compact transition capture keeps one committed state
and records only the information needed to reconstruct an accepted
prefix.
The schema intentionally exposes only native arithmetic and does not
include the experimental `arithmetic_mode` attribute. Models exported
with the retired experimental ABI must be re-exported.
Companion ONNX Runtime GenAI integration:
https://github.com/microsoft/onnxruntime-genai/pull/2472
### Validation
- `./build/cu130/Debug/onnxruntime_provider_test
--gtest_filter='*GatedDeltaNet*'`
- 26/26 focused tests passed on H200 with CUDA 13.0 and cuDNN 9.23.
### Performance and Quality
On H200, context 2048, generation 256, with five paired fresh-process
repetitions per batch:
- Native arithmetic won all 40 MTP and DFlash2 throughput pairs versus
the retired compatibility experiment. Median native/compatibility ratios
were 1.0519 for MTP and 1.0543 for DFlash2.
- Paired quality differences were not statistically significant:
MMLU-Pro 83.75% native vs. 83.38% compatibility (McNemar p=0.73); GPQA
81.82% vs. 78.28% (p=0.23).
- Against the retired separate-factor representation, the packed capsule
preserved exact tokens and replay work. It won 20/20 MTP pairs and was
at parity for DFlash2 batch 16, with a small-batch benefit.
