[justinchuby]

Native CPU EP op-coverage fixes surfaced by audio models

While bringing up Whisper and Nemotron ASR (Foundry Local) on the native CPU EP, two general, well-scoped correctness/harness gaps surfaced. This PR lands those; the audio models themselves remain blocked on unimplemented com.microsoft::Attention / MHA / LSTM kernels (tracked separately).

Fixes

1. Signed-integer Neg (onnx-runtime-ep-cpu unary_math): Neg on Int32/Int64 now routes through wrapping_neg (matches ONNX two's-complement overflow semantics, incl. Neg(INT_MIN) == INT_MIN); float path unchanged. Non-vacuous regression test covers the MIN wrap for both widths.
2. Int32 bench inputs (onnx-genai-bench bench_generic): the generic native-vs-ORT harness can now synthesize Int32 model inputs, so integer-input graphs benchmark and parity-check instead of erroring.

Scope note

A third commit from the audio bring-up (a com.microsoft::MultiHeadAttention shape-inference rule) was rejected in review for mishandling differing value head_size and is being reworked separately — deliberately excluded here.

Review

Non-author review by Hicks: commits 1+2 🟢 APPROVED (the rejection applied only to the excluded MHA commit).

Gates: ep-cpu tests incl. neg_supports_signed_integer_tensors, ep-cpu clippy (mlas), fmt (only pre-existing mlas-sys:1211 artifact) — green. (Pre-existing onnx-genai-engine clippy nits under the bench-native feature are outside CI's path and untouched here.)

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

[codecov]

Codecov Report

❌ Patch coverage is 92.68293% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.49%. Comparing base (7d5ad92) to head (08021ff).

Files with missing lines	Patch %	Lines
...ates/onnx-runtime-ep-cpu/src/kernels/unary_math.rs	92.68%	0 Missing and 3 partials ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #115   +/-   ##
=======================================
  Coverage   82.49%   82.49%           
=======================================
  Files         231      231           
  Lines       99760    99799   +39     
  Branches    99760    99799   +39     
=======================================
+ Hits        82296    82333   +37     
  Misses      14074    14074           
- Partials     3390     3392    +2     

Files with missing lines	Coverage Δ
...ates/onnx-runtime-ep-cpu/src/kernels/unary_math.rs	88.93% <92.68%> (+1.23%)	⬆️

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