ci: add benchmark workflow

.github/scripts/run_benchmarks.sh

@@ -0,0 +1,39 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+mkdir -p benchmark-results
+benchmark_json="${BENCHMARK_JSON:-benchmark-results/current.json}"
+benchmark_dir="${BENCHMARK_HYPERFINE_DIR:-tests/benchmarks/hyperfine}"
+
+shopt -s nullglob
+benchmark_scripts=("$benchmark_dir"/benchmark_*.sh)
+shopt -u nullglob
+
+if [ "${#benchmark_scripts[@]}" -eq 0 ]; then
+  echo "No hyperfine benchmark scripts matching benchmark_*.sh found in $benchmark_dir" >&2
+  exit 1
+fi
+
+echo "Benchmark Python: $(command -v python)"
+python -c 'import sys; print(sys.version)'
+
+commands=()
+names=()
+for benchmark_script in "${benchmark_scripts[@]}"; do
+  title="$(sed -n 's/^# BENCHMARK_TITLE:[[:space:]]*//p' "$benchmark_script" | head -n 1)"
+  if [ -z "$title" ]; then
+    title="$(basename "$benchmark_script" .sh)"
+  fi
+  echo "Preflight benchmark script: $benchmark_script"
+  bash "$benchmark_script"
+  names+=(--command-name "$title")
+  commands+=("bash $(printf "%q" "$benchmark_script")")
+done
+
+hyperfine \
+  --show-output \
+  --warmup 1 \
+  --runs 5 \
+  "${names[@]}" \
+  --export-json "$benchmark_json" \
+  "${commands[@]}"