Strata v0.1.18

Clearer engine updates, a `SETUP.bat` shortcut, and a sampler guard.

• Updating right after a release no longer keeps the old engine without saying why (#58, thanks @XeonG). New files on main could reach you a few minutes before the release's engine finished uploading; setup then kept the installed engine with only a short warning. Releases are now published together with the engine, and if it ever happens again setup says the new engine isn't published yet and to run it again in a few minutes.
• `SETUP.bat`: double-click it to change settings or install another model (the same as START-HERE.bat --setup; on Linux ./setup.sh --setup).
• Sampler: with the penalty window set to 0, the sampling kernel no longer touches its (then empty) penalty buffer when a caller still passes a token history (#59, thanks @j-luwierski). The server never does this, so answers are unchanged; it's a guard for other callers of the kernel.

Updating: get the latest files (git pull, or download and unzip anywhere), then run START-HERE.bat. An existing 0.1.17 engine keeps working (nothing in this release needs the new one); a new install gets 0.1.18. On Linux, run ./setup.sh.

The ready-made Strata engine for Windows (RTX 30 / 40 / 50: sm_86, sm_89, sm_120 + PTX), CUDA 13.0.

You don't need to download this yourself: START-HERE.bat fetches it (and NVIDIA's cuBLAS from pip), so no compiler or CUDA Toolkit is needed, only an NVIDIA driver 580 or newer.

Contents: strata.exe (the engine), strata-vision.exe (the optional image encoder), BUILD.json.