Add README section about setting up Wine 9.21

README.md

@@ -92,6 +92,32 @@ replacing the system Wine package. The wrapper expects Wine to be extracted at:
 $HOME/.local/opt/wine-staging-9.21
 ```
 
+Install that local Wine tree from the Arch Linux Archive package:
+
+```sh
+mkdir -p "$HOME/.local/opt/wine-staging-9.21"
+
+curl -L -o /tmp/wine-staging-9.21-1-x86_64.pkg.tar.zst \
+  "https://archive.archlinux.org/packages/w/wine-staging/wine-staging-9.21-1-x86_64.pkg.tar.zst"
+
+bsdtar -C "$HOME/.local/opt/wine-staging-9.21" \
+  -xf /tmp/wine-staging-9.21-1-x86_64.pkg.tar.zst
+```
+
+This intentionally does not install or downgrade the system Wine package. The
+archive is unpacked into a private directory with the package's normal `usr/`
+layout:
+
+```text
+$HOME/.local/opt/wine-staging-9.21/usr/bin/wine64
+$HOME/.local/opt/wine-staging-9.21/usr/bin/wineserver
+$HOME/.local/opt/wine-staging-9.21/usr/lib/wine
+```
+
+Do not add this Wine directory to the global shell `PATH`. Use
+`scripts/wine-staging-9.21.sh` so only plugin installation, plugin maintenance,
+yabridge syncs, and the Bitwig yabridge launcher use this Wine version.
+
 Verify the wrapper before using it:
 
 ```sh