Fix portable project build

[Sean-Kenneth-Doherty]

Problem

The project file does not build cleanly outside a Windows/Visual Studio layout. On Linux with KSP 1.12.5 assemblies, xbuild stops before compilation because SolarScience.csproj unconditionally imports the Visual Studio TextTemplating targets path:

SolarScience.csproj could not import "$(MSBuildExtensionsPath)\Microsoft\VisualStudio\v17.0\TextTemplating\Microsoft.TextTemplating.targets"

The project also references Properties\Version.cs, while the tracked generated file is Properties\version.cs, which breaks on case-sensitive filesystems.

Changes

• Uses the tracked Properties\version.cs filename in the project file.
• Makes the TextTemplating targets import and TextTransform.exe pre-build step conditional.
• Makes the Windows deploy/release post-build hook conditional so a source build can write to an explicit output folder when the batch files are absent.

This is intentionally build-only; no runtime C# source files are changed.

Validation

Environment: KSP 1.12.5.3190 assemblies from Steam, Mono/xbuild 14.0 on Linux.

• origin/master project file: fails before compilation with the missing TextTemplating targets import.
• This branch:

xbuild source/SolarScience.csproj \
  /p:Configuration=Release \
  /p:K112="/home/sean/.local/share/Steam/steamapps/common/Kerbal Space Program/KSP_Data/Managed/" \
  /p:OutputPath="/home/sean/Projects/ksp-mod-updates/artifacts/SolarScience-proof/portable-build/" \
  /p:PostBuildEvent= \
  /verbosity:minimal

Build result: succeeded, producing SolarScience.dll with SHA-256 f3d894d6296f62df7af4ffc1413cbf2c0a0eac6ac27d19c8902e591f58dc5baa.

Additional KSP load check: installed that DLL into a disposable KSP 1.12.5.3190 GameData with SolarScience assets. A proof addon reached MainMenu, found both KMI and STEREO, called their module startup path, loaded both opening audio clips, and reported OVERALL result=PASS. The log had no NullReferenceException, TypeLoadException, or MissingMethodException.

[Sean-Kenneth-Doherty]

Closing this under my tightened quality bar rather than leaving a source-build-only draft in your queue. The branch has useful local build/load checks, but there is no current issue or maintainer request behind it, and it does not change runtime behavior. I will not reopen unless there is a concrete maintainer-requested build/release need or a player-facing defect with proof.