AiterAsmKernel: add init-time sanity checks for .co registration

[alexioslyrakis-amd]

Summary

• Adds validate_hsaco_lds() to AiterAsmKernelFast::init(): scans the raw .co ELF blob for group_segment_fixed_size via msgpack decode and checks it against the device LDS limit (hipDeviceGetAttribute). Fires before registration, giving an actionable error instead of a silent null from hipGetFuncBySymbol.
• Adds a registration probe in init(): since __hipRegisterFunction returns void, a hipGetFuncBySymbol probe detects silent rejection by the runtime (LDS limit exceeded, arch mismatch, corrupted binary, etc.).
• Both checks run once per kernel variant at construction time — zero impact on the launch_kernel() hot path.

Motivation

On gfx942 (MI300X) the LDS limit is 64 KB. A .co built targeting gfx950 (MI355X, ~160 KB LDS) would be silently rejected at registration, hipGetFuncBySymbol would return null, and hipModuleLaunchKernel would emit only a generic hipErrorIllegalState with no indication of the root cause.

Test plan

• Run with a .co declaring group_segment_fixed_size > 65536 on gfx942 — expect clear error from validate_hsaco_lds() at init
• Run with a correctly built .co on gfx942 — expect no error, kernel executes normally

[github-actions]

🏷️ CI Guide

Runs automatically on every PR:

• ✅ Pre-checks (submodule verification, code formatting)
• ✅ Aiter op tests (gfx942 + gfx950)
• ✅ Triton tests on MI35X (only when aiter/ops/triton/** or related paths are changed)

Extended tests (opt-in via labels):

Label	Tests
ci:triton-300x	Run an additional Triton test job on MI300X in PRs; main branch always runs both MI35X and MI300X
ci:sglang	SGLang integration tests: DeepSeek-R1-MXFP4 accuracy, Qwen 3.5 accuracy
ci:atom	ATOM benchmark: DeepSeek-R1-0528, GPT-OSS-120B
ci:atom_full	ATOM accuracy suite for PR and main models from ATOM models_accuracy.json
ci:vllm	vLLM benchmark: GPT-OSS-120B, DeepSeek-R1-0528, Kimi-K2.5
ci:all	All standard extended tests (excludes ci:atom_full)

Only add ci:atom_full for FlyDSL or Triton upgrades.
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