feat: Add ZImage/LongCat/Sana diffusion support + LLM VL improvements…

[er6y]

… + OpenCL fixes

Diffusion Engine:

• Add ZImageDiffusion subclass: FlowMatch Euler scheduler, PhiloxRNG noise, CLIP text encoder
• Add LongCatDiffusion subclass: LLM text encoder (lazy load), Flux-like latent packing, VAE enc/dec, T2I + Image Edit modes
• Integrate SanaDiffusion with SanaLlm into unified API, fix Euler sampling (dt/1000->dt) and CFG order
• Add DiffusionConfig/LLMEncoderConfig, GPU config (BUFFER mode, FP32, Memory_Low, OpenCL cache)
• Add DiffusionGpuMemoryMode/PrecisionMode/CFGMode enums
• Extend createDiffusion factory with full parameters for all model types
• Unify diffusion_demo to support SD1.5/Taiyi/Sana/ZImage/LongCat with cfg_scale and input_image args
• Add image processing utilities (resize, crop, colorspace, pack/unpack latents)
• Implement FlowMatchEuler scheduler

LLM / Vision:

• omni.cpp: Qwen3-VL vision fixes (floor rounding, nullptr check)
• omni.hpp: mrope position ids fix max(T,H,W)+1
• tokenizer.hpp: public wrapper header, MNN_PUBLIC export
• llm_demo: LLM_DEMO_ONELINE mode
• pymnn llm.h: forward_all() binding
• Fix Qwen2_5Vision transformer_fuse for window attention compatibility

OpenCL fixes:

• BinaryBufExecution: localWorkSize divisibility check
• binary_buf.cl: float4/int4 init, per-element ReLU (NVIDIA compiler bug workaround)

Other fixes:

• ShapeSliceTf/ShapeWhere: shape calculation rewrite
• OnnxEinsum: outer product broadcast _Unsqueeze fix
• Pipeline: NaN/Inf debug check macro (disabled by default)
• Fix LongCat unpackLatentsGPU to match master implementation

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