careless: build venv with uv instead of conda (anaconda.com blocked on Ra)

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

careless/build

@@ -5,12 +5,11 @@ pbuild::prep() {
 }
 
 pbuild::configure() {
-    # careless is pip-installed, but upstream recommends a fresh conda env
-    # (TensorFlow dependency conflicts), so install a private miniconda in PREFIX
-    mkdir -p "$PREFIX/miniconda"
-    wget https://repo.anaconda.com/miniconda/Miniconda3-latest-Linux-x86_64.sh -O "$PREFIX/miniconda/miniconda.sh"
-    bash "$PREFIX/miniconda/miniconda.sh" -b -u -p "$PREFIX/miniconda/"
-    "$PREFIX/miniconda/condabin/conda" create -y -n "careless_$V" python=3.12
+    # repo.anaconda.com is unreachable from Ra (GnuTLS error), so no conda.
+    # uv fetches a standalone CPython instead; keep it inside PREFIX so the
+    # venv's interpreter symlinks don't depend on the builder's home cache.
+    export UV_PYTHON_INSTALL_DIR="$PREFIX/python"
+    uv venv --python 3.12 "$PREFIX/venv"
 }
 
 pbuild::compile() {
@@ -18,10 +17,6 @@ pbuild::compile() {
 }
 
 pbuild::install() {
-    source "$PREFIX/miniconda/etc/profile.d/conda.sh"
-    conda activate "careless_$V"
-    pip install --upgrade pip
     # [cuda] extra ships the NVIDIA libs via pip wheels; works on CPU-only nodes too
-    pip install --no-cache-dir "careless[cuda]==${V_PKG}"
-    conda deactivate
+    uv pip install --python "$PREFIX/venv/bin/python" "careless[cuda]==${V_PKG}"
 }