Add Windows cross-build and Gitea release; share CI setup

- just windows-deps / windows / package-windows: cross-compile with Odin
  objects + lld-link against an xwin SDK, static VC runtime
- Release workflow runs on v* tags, builds Linux and Windows packages,
  uploads them to the package registry and creates a Gitea release
- Shared toolchain setup as a local composite action

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

justfile

@@ -1,5 +1,13 @@
 name := "HanjaKanaMun"
 build_dir := "build"
+odin_version := "dev-2026-09"
+xwin_version := "0.10.0"
+
+# Windows cross-compilation inputs (see `windows-deps`)
+xwin := env("XWIN", build_dir / "xwin")
+xwin_sdk := env("XWIN_SDK", build_dir / "xwin-sdk")
+raylib_windows := env("RAYLIB_WINDOWS", build_dir / "raylib-windows")
+lld_link := env("LLD_LINK", "lld-link")
 
 # List available recipes
 default:
@@ -22,17 +30,65 @@ test:
     mkdir -p {{build_dir}}
     odin test tests -vet -define:ODIN_TEST_THREADS=1 -out:{{build_dir}}/tests
 
-# Optimized build into build/, with the assets it needs at runtime
+# Optimized native build into build/<os>/, with the assets it needs at runtime
 release:
-    mkdir -p {{build_dir}}/{{name}}
-    odin build . -vet -o:speed -out:{{build_dir}}/{{name}}/{{name}}
-    cp -R assets {{build_dir}}/{{name}}/
+    mkdir -p {{build_dir}}/{{os()}}/{{name}}
+    odin build . -vet -o:speed -out:{{build_dir}}/{{os()}}/{{name}}/{{name}}
+    cp -R assets {{build_dir}}/{{os()}}/{{name}}/
 
-# Release build packed as build/<name>_<version>_<os>_<arch>.tar.gz
+# Native release build packed as build/<name>_<version>_<os>_<arch>.tar.gz
 package version="dev": release
-    tar -czf {{build_dir}}/{{name}}_{{version}}_{{os()}}_{{arch()}}.tar.gz -C {{build_dir}} {{name}}
+    tar -czf {{build_dir}}/{{name}}_{{version}}_{{os()}}_{{arch()}}.tar.gz -C {{build_dir}}/{{os()}} {{name}}
     @echo "{{build_dir}}/{{name}}_{{version}}_{{os()}}_{{arch()}}.tar.gz"
 
+# Download the Windows SDK + CRT (via xwin, accepting Microsoft's license) and raylib.lib. Linux x86_64 only.
+windows-deps:
+    #!/usr/bin/env bash
+    set -euo pipefail
+    mkdir -p {{build_dir}}
+    if [ ! -x "{{xwin}}" ]; then
+        curl -fsSL https://github.com/Jake-Shadle/xwin/releases/download/{{xwin_version}}/xwin-{{xwin_version}}-x86_64-unknown-linux-musl.tar.gz \
+            | tar -xz -C {{build_dir}} --strip-components=1 xwin-{{xwin_version}}-x86_64-unknown-linux-musl/xwin
+    fi
+    if [ ! -d "{{xwin_sdk}}/crt" ]; then
+        "{{xwin}}" --accept-license --arch x86_64 --cache-dir {{build_dir}}/xwin-cache splat --output "{{xwin_sdk}}"
+    fi
+    # Odin's Linux/macOS releases don't ship raylib's Windows library, so take it from the Windows release
+    if [ ! -f "{{raylib_windows}}/raylib.lib" ]; then
+        mkdir -p "{{raylib_windows}}"
+        curl -fsSL -o {{build_dir}}/odin-windows.zip \
+            https://github.com/odin-lang/Odin/releases/download/{{odin_version}}/odin-windows-amd64-{{odin_version}}.zip
+        unzip -o -j {{build_dir}}/odin-windows.zip 'dist/vendor/raylib/windows/raylib.lib' -d "{{raylib_windows}}"
+    fi
+
+# Cross-compile a Windows x86_64 build into build/windows/ (run `just windows-deps` first)
+windows:
+    #!/usr/bin/env bash
+    set -euo pipefail
+    obj_dir={{build_dir}}/obj-windows
+    out_dir={{build_dir}}/windows/{{name}}
+    mkdir -p "$obj_dir" "$out_dir"
+    rm -f "$obj_dir"/*.obj
+    odin build . -vet -o:speed -target:windows_amd64 -build-mode:obj -out:"$obj_dir/{{name}}.obj"
+    # Odin can't link for Windows from other platforms, so link with lld-link.
+    # The VC runtime is linked statically (no VCRUNTIME140.dll needed); the
+    # Universal CRT is used from Windows itself (built into Windows 10+).
+    {{lld_link}} /nologo /machine:x64 /subsystem:windows /entry:mainCRTStartup \
+        /out:"$out_dir/{{name}}.exe" "$obj_dir"/*.obj "{{raylib_windows}}/raylib.lib" \
+        /libpath:"{{xwin_sdk}}/crt/lib/x86_64" \
+        /libpath:"{{xwin_sdk}}/sdk/lib/um/x86_64" \
+        /libpath:"{{xwin_sdk}}/sdk/lib/ucrt/x86_64" \
+        /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
+    cp -R assets "$out_dir/"
+
+# Windows build packed as build/<name>_<version>_windows_x86_64.zip
+package-windows version="dev": windows
+    cd {{build_dir}}/windows && zip -qr ../{{name}}_{{version}}_windows_x86_64.zip {{name}}
+    @echo "{{build_dir}}/{{name}}_{{version}}_windows_x86_64.zip"
+
 # Format all Odin files with odinfmt (settings in odinfmt.json)
 fmt:
     odinfmt -w .