fix: set MATLABROOT env var for Engine install from temp copy

The MATLAB Engine setup.py walks up the directory tree to find the
MATLAB root. When source is copied to %TEMP%, that relative path
breaks with "installation is corrupted". Setting MATLABROOT tells
setup.py exactly where MATLAB is.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: HanSur94

install.bat

@@ -258,6 +258,9 @@ if %errorlevel% equ 0 (
         goto :install_mcp
     )
     echo  Building and installing MATLAB Engine API...
+    :: Set MATLABROOT so setup.py can find MATLAB (it normally walks up
+    :: from its own directory, which breaks when copied to temp)
+    set "MATLABROOT=!MATLAB_ROOT!"
     pip install "!ENGINE_TEMP!" --no-build-isolation --quiet 2>&1
     if !errorlevel! neq 0 (
         echo.