use common cache dir to save disk space and time

careless/build

@@ -11,7 +11,7 @@ pbuild::configure() {
     # modbuild's shell strips ~/.local/bin from PATH; override with UV=/path/to/uv if needed
     UV="${UV:-$HOME/.local/bin/uv}"
     # ~/.cache/uv hits the home disk quota; cache under PREFIX (removed after install)
-    export UV_CACHE_DIR="$PREFIX/.uv-cache"
+    export UV_CACHE_DIR="/opt/psi/MX/.uv-cache"
     export UV_PYTHON_INSTALL_DIR="$PREFIX/python"
     "$UV" venv --python 3.12 "$PREFIX/venv"
 }
@@ -22,8 +22,7 @@ pbuild::compile() {
 
 pbuild::install() {
     UV="${UV:-$HOME/.local/bin/uv}"
-    export UV_CACHE_DIR="$PREFIX/.uv-cache"
+    export UV_CACHE_DIR="/opt/psi/MX/.uv-cache"
     # [cuda] extra ships the NVIDIA libs via pip wheels; works on CPU-only nodes too
     "$UV" pip install --python "$PREFIX/venv/bin/python" "careless[cuda]==${V_PKG}"
-    rm -rf "$UV_CACHE_DIR"
 }