careless: put uv cache under PREFIX, home quota too small for TF wheels

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

careless/build

@@ -10,6 +10,8 @@ pbuild::configure() {
     # venv's interpreter symlinks don't depend on the builder's home cache.
     # 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="$PREFIX/.uv-cache"
     export UV_PYTHON_INSTALL_DIR="$PREFIX/python"
     "$UV" venv --python 3.12 "$PREFIX/venv"
 }
@@ -20,6 +22,8 @@ pbuild::compile() {
 
 pbuild::install() {
     UV="${UV:-$HOME/.local/bin/uv}"
+    export UV_CACHE_DIR="$PREFIX/.uv-cache"
     # [cuda] extra ships the NVIDIA libs via pip wheels; works on CPU-only nodes too
     "$UV" pip install --python "$PREFIX/venv/bin/python" "careless[cuda]==${V_PKG}"
+    rm -rf "$UV_CACHE_DIR"
 }