Polish onboarding and reference asset layout

scripts/prepare_dev_worktree.sh

@@ -38,6 +38,10 @@ fi
 
 echo "[4/6] Copying local runtime env when available"
 copy_optional_path ".env"
+if [[ ! -f "${DEV_DIR}/.env" && -f "${DEV_DIR}/.env.example" ]]; then
+  cp "${DEV_DIR}/.env.example" "${DEV_DIR}/.env"
+  echo "Created ${DEV_DIR}/.env from .env.example"
+fi
 
 echo "[5/6] Copying local-only incoming design assets when available"
 copy_optional_path "incoming-files/1.png"