chat: trim messages sent to StepFun parser (fixes long reasoning loops) (#25238) chat: trim messages sent to StepFun parser (fixes long reasoning loops) add regression test; remove duplicate template chat: trim StepFun content parts before rendering The StepFun trim workaround ran on the already-rendered messages, where typed content parts have been concatenated into a single string, so the per-part whitespace could no longer be reached. Move the trim ahead of rendering and apply it to content_parts text as well as the string content and reasoning_content. Adds a content-parts regression test.

Co-Authored-By: Piotr Wilkin Assisted-By: Claude Fable 5 --------- Co-authored-by: tarruda 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 7.2) 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…