v1.2.2

Ship the plugin system with a build that survives parallel compilation

The library was compiled twice under two global-property sets, so a parallel
solution build raced on its own obj/ directory and failed with CS2012/MSB3713.  The
native set now comes from the library's own RuntimeIdentifier, which is what CI was
tripping over.

Plugins get a directory each under a common parent, loaded in dependency order, and
the release ships the tracked ones inside <exe>/Plugins on both platforms -- published
framework-dependent, so a package is 60 MB instead of 130 MB with three copies of the
runtime.  The loader identifies a native library by its header rather than its path,
so the flattened layout no longer logs BadImageFormat at startup.

The export gained a material for shaders the game ships none for, a material index,
and a render-test route that draws every recovered shader against real pictures.