GeminiWatermarkTool

v0.2.8 - macOS Vulkan Loader Crash Hot-Fix

Hot-fix release for SIGBUS crashes on macOS Apple Silicon reported in
v0.2.7 (issues #30 and #31). The same root cause has been latent since
the AI denoise feature was introduced in earlier 0.2.x releases; only
v0.2.7's broader distribution surfaced it.

macOS Vulkan Loader Crash:

• Probe libvulkan.1.dylib / libvulkan.dylib via dlopen before calling
  NCNN's create_gpu_instance(); skip the GPU init path entirely when
  the loader is absent
• Previously, NCNN's internal simplevk silently failed dlopen and
  create_gpu_instance() then dispatched through uninitialised
  function pointers, causing SIGBUS (instruction abort in .data
  segment) on macOS without MoltenVK installed
• macOS users without MoltenVK / LunarG Vulkan SDK now correctly
  fall back to CPU inference instead of crashing
• The platform-specific probe also covers Windows (vulkan-1.dll) and
  Linux (libvulkan.so.1 / libvulkan.so) -- behaviour unchanged on
  systems where the loader is present
• Tailored log message names MoltenVK and the LunarG Vulkan SDK so
  macOS users have a clear remediation path
• Refs #30, #31

CI Smoke Test:

• New scripts/ci_smoke_ai_denoise.sh generates a 512x512 PNG and
  runs the binary with --force --region br:auto --denoise ai end
  to end
• Wired into all six build jobs (full + gwt-mini, across Windows /
  Linux / macOS) after the existing --version check
• Exercises NcnnDenoiser::initialize() and would have caught these
  issues on the macOS runner immediately. The plain --version
  smoke test we had previously did not touch this code path

macOS CPU Fallback Performance:

• The CPU code path is fully functional but considerably slower
  than Vulkan GPU inference (around 650 ms for a 112x112 ROI on
  the GitHub Actions macOS runner; native Apple Silicon hardware
  is faster but still well below dGPU performance)
• Users wanting GPU acceleration on macOS can install the LunarG
  Vulkan SDK, which includes a Vulkan loader and MoltenVK. The
  longer-term plan is to ship MoltenVK inside the macOS bundle in
  a future v0.3.x release so no user setup is required

Upgrade Notes:

• v0.2.8 is a strict superset of v0.2.7: same CLI flags, same
  artifacts (full + gwt-mini for Windows / Linux / macOS), same
  behaviour on platforms where the Vulkan loader is available
• macOS users on v0.2.7 who hit the SIGBUS crash should upgrade
  directly to v0.2.8