home: direnv: add 'layout_uv'

I haven't really played with it yet, but from my small experiments this
should be good enough for my (future) purposes.

modules/home/direnv/lib/python.sh

@@ -23,3 +23,34 @@ layout_poetry() {
     watch_file pyproject.toml
     watch_file poetry.lock
 }
+
+layout_uv() {
+    if ! has uv; then
+        # shellcheck disable=2016
+        log_error 'layout_uv: `uv` is not in PATH'
+        return 1
+    fi
+
+    if [[ ! -f pyproject.toml ]]; then
+        # shellcheck disable=2016
+        log_error 'layout_uv: no pyproject.toml found. Use `uv init` to create one first'
+        return 1
+    fi
+
+    local default_venv="$PWD/.venv"
+    : "${VIRTUAL_ENV:=$default_venv}"
+
+    # Use non-default venv path if required
+    if [ "$VIRTUAL_ENV" != "$default_venv" ]; then
+        export UV_PROJECT_ENVIRONMENT="$VIRTUAL_ENV"
+    fi
+
+    # create venv if it doesn't exist
+    uv venv -q
+
+    export VIRTUAL_ENV
+    export UV_ACTIVE=1
+    PATH_add "$VIRTUAL_ENV/bin"
+    watch_file pyproject.toml
+    watch_file uv.lock
+}