FluidX3D — von Kármán vortex street, headless GRAPHICS export

Same solver the benchmark event scores (2,834/2,787 MLUPs/s, D3Q19 FP16S) -- this build flips GRAPHICS on instead of BENCHMARK and runs a real simulation: flow past a cylinder in a duct (Re 25,000), flag wireframe + Q-criterion isosurface coloured by velocity, no window/X11 (write_frame() straight to disk).

cloud: GCP Cloud Run, europe-west4, NVIDIA L4 · job: fluidx3d-viz · execution: fluidx3d-viz-5tl4r · date: 2026-09-02 · image digest: sha256:df05d4fb...dcd59f27 · FluidX3D commit aba9413 · own RESULT payload: 30 frames, 31/31 uploaded, 16 s wall · geometry/flow parameters copied verbatim from upstream's own "cylinder in rectangular duct" example; the GRAPHICS export loop is new, adapted from upstream's "Boeing 747" example (the one pattern in setup.cpp written for headless export) · first attempt (execution fluidx3d-viz-6dj82) produced near-blank frames -- a hand-picked free-camera position was pointed at empty space (measured: 2 colours, 723/522717 px lit); fixed by switching to set_camera_centered, which auto-fits the box · hero built by the Visuals Lead