b10707

kv-cells: stop the sequence scan once all sequences are seen (#28011)

for_each_token_in tested all LLAMA_MAX_SEQ sequences for every used cell,
while a cell almost always belongs to one. The scan now stops once the
cell's own sequences have been seen. Same visit order, same callback
arguments, so behaviour is unchanged.

get_prev_tokens is the only caller, so this affects the n-gram path.

RTX PRO 6000, Qwen3.8-Flash-Next UD-Q4_K_XL, fa on, warm runs:

55k context generation 56.3 -> 74.3 t/s
132k context generation 33.6 -> 50.9 t/s

Prompt processing is unchanged, the scan is amortised over the ubatch
there. The gain follows the number of used cells, so it grows with
context and is invisible on short prompts.

Website:

• https://llama.app

Attestations:

• https://github.com/ggml-org/llama.cpp/attestations/44036640

macOS/iOS:

• macOS Apple Silicon (arm64)
• macOS Apple Silicon (arm64, KleidiAI enabled) DISABLED
• macOS Intel (x64)
• iOS XCFramework

Linux:

• Ubuntu x64 (CPU)
• Ubuntu arm64 (CPU)
• Ubuntu s390x (CPU)
• Ubuntu x64 (Vulkan)
• Ubuntu arm64 (Vulkan)
• Ubuntu x64 (ROCm 7.14)
• Ubuntu x64 (OpenVINO)
• Ubuntu x64 (SYCL FP32)
• Ubuntu x64 (SYCL FP16)

Android:

• Android arm64 (CPU)

Windows:

• Windows x64 (CPU)
• Windows arm64 (CPU)
• Windows arm64 (OpenCL Adreno)
• Windows x64 (CUDA 12) - CUDA 12.4 DLLs
• Windows x64 (CUDA 13) - CUDA 13.3 DLLs
• Windows arm64 (CUDA 13) (preview) - CUDA 13.4 DLLs
• Windows x64 (Vulkan)
• Windows x64 (OpenVINO)
• Windows x64 (SYCL)
• Windows x64 (ROCm 7.14)

openEuler:

• DISABLED
• openEuler x86 (310p)
• openEuler x86 (910b, ACL Graph)
• openEuler aarch64 (310p)
• openEuler aarch64 (910b, ACL Graph)

UI:

• UI