Windows build links ole32; CI cross-builds Windows on main/develop; docs

- os.user_data_dir needs ole32.lib on Windows
- Build workflow gets a Windows cross-build job with a cached SDK
- Drop the backtick from Jua's codepoints (the font lacks it)
- Update AGENTS.md and README for decks, controls, scores and layout

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

justfile

@@ -81,7 +81,7 @@ windows:
         /nodefaultlib:msvcrt /nodefaultlib:vcruntime /nodefaultlib:libucrt \
         libcmt.lib libvcruntime.lib ucrt.lib \
         kernel32.lib user32.lib gdi32.lib winmm.lib shell32.lib opengl32.lib \
-        advapi32.lib bcrypt.lib ntdll.lib synchronization.lib
+        advapi32.lib bcrypt.lib ntdll.lib synchronization.lib ole32.lib
     cp -R assets "$out_dir/"
 
 # Windows build packed as build/<name>_<version>_windows_x86_64.zip