SimSat v0.1.6 - faster GPU preview and improved top-down clouds

Highlights

• Adds a one-click GPU Render action in SimSat Studio. Rust, the CLI, and
  Python now expose the same explicit gpu-preview backend, and every temporary
  compatibility substitution is reported rather than silently ignored.
• Adds real GPU cloud rendering for top-down views.
• Top-down output now honors Model native, ABI 1 km, and ABI 2 km
  resolution while preserving the model domain's physical aspect ratio at the
  output-size cap. Model native means one pixel per source-grid cell.
• Adds an opt-in, default-off top-down stratiform reconstruction control for
  source-grid ring artifacts in affected HRRR cloud fields. It is available in
  Studio, the CLI, Python, and Rust; geostationary and raw-band rendering remain
  unchanged.
• Adds opt-in bounded delta-flux cloud-transport modes, including the
  brightness-neutral delta-flux-v2b experiment.
• Windows executables now carry correct embedded FileVersion/ProductVersion
  metadata (0.1.6).

The v0.1.5 visible calibration remains in place: exposure 1.5, cloud optical
depth scale 0.15, brighter terrain presentation, and finite-domain cloud-edge
feathering.

Validation

• Public Linux CI passed: fmt, strict clippy, and the full workspace test suite.
• Release-artifact builds passed on Windows and Linux.
• The published Windows executable is the exact locally tested static-CRT RC.
• The manylinux wheel passed a clean WSL import/version smoke.
• Both packaged Linux CLI binaries retained mode 0755 and passed --help.

Build records: CI and release artifacts.

SHA-256

57282CDFE177224FB6EB3D2CE30AAF02BEDD4C3925DE7809B060F8CAB92245F9  simsat-0.1.6-cp38-abi3-manylinux_2_17_x86_64.manylinux2014_x86_64.whl
4AACDD56FFEDB3D46B9818857F977421A0C72A7392C00EEEE264B935BD388E4B  simsat-cli-v0.1.6-linux-x86_64.tar.gz
56D9C18AD30BC0743C13F7E75A269036D457A7F631CD21094814A862003DBAB3  simsat-studio-v0.1.6-windows-x86_64.exe
66B16FC0C7353CB519114C2B2C338FF32CFD1B2CF41431ECA62EC5FDBB5319FF  THIRD-PARTY-NOTICES.txt

The Windows executable is currently unsigned, so Microsoft Defender
SmartScreen may show an Unknown publisher warning. Verify the SHA-256 above
before running it.