chore: import upstream snapshot with attribution

scripts/coverage.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+# Copyright 2026 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+set -euo pipefail
+
+# Check if cargo-llvm-cov is installed
+if ! cargo llvm-cov --version &> /dev/null; then
+  echo "cargo-llvm-cov is not installed. Installing..."
+  cargo install cargo-llvm-cov
+fi
+
+# Run coverage and generate HTML report
+echo "Running tests with coverage..."
+cargo llvm-cov --all-features --workspace --html
+cargo llvm-cov --all-features --workspace # Print text summary
+
+echo "Coverage report generated at target/llvm-cov/html/index.html"
+
+# Open the report if on macOS
+if [[ "$OSTYPE" == "darwin"* ]]; then
+  open target/llvm-cov/html/index.html
+fi