[Autoloop: perf-comparison] Iteration 407: add toExcel benchmark pair

Run: https://github.com/githubnext/tsb/actions/runs/29625071540

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: github-actions[bot]

benchmarks/pandas/bench_to_excel.py

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+"""Benchmark: to_excel — write a DataFrame to an XLSX buffer (BytesIO)."""
+import json, time, io
+import pandas as pd
+
+ROWS = 5_000
+WARMUP = 3
+ITERATIONS = 20
+
+df = pd.DataFrame({
+    "name": [f"name_{i % 1000}" for i in range(ROWS)],
+    "value": [i * 1.5 for i in range(ROWS)],
+    "flag": [i % 2 == 0 for i in range(ROWS)],
+})
+
+for _ in range(WARMUP):
+    buf = io.BytesIO()
+    df.to_excel(buf, index=True)
+
+times = []
+for _ in range(ITERATIONS):
+    buf = io.BytesIO()
+    t0 = time.perf_counter()
+    df.to_excel(buf, index=True)
+    times.append((time.perf_counter() - t0) * 1000)
+
+total_ms = sum(times)
+print(json.dumps({"function": "to_excel", "mean_ms": round(total_ms / ITERATIONS, 3), "iterations": ITERATIONS, "total_ms": round(total_ms, 3)}))

benchmarks/tsb/bench_to_excel.ts

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+/**
+ * Benchmark: toExcel — serialize a DataFrame to an XLSX binary buffer.
+ * Outputs JSON: {"function": "to_excel", "mean_ms": ..., "iterations": ..., "total_ms": ...}
+ */
+import { DataFrame, toExcel } from "../../src/index.ts";
+
+const ROWS = 5_000;
+const WARMUP = 3;
+const ITERATIONS = 20;
+
+const index = Array.from({ length: ROWS }, (_, i) => i);
+const colA = Array.from({ length: ROWS }, (_, i) => `name_${i % 1000}`);
+const colB = Array.from({ length: ROWS }, (_, i) => i * 1.5);
+const colC = Array.from({ length: ROWS }, (_, i) => i % 2 === 0);
+
+const df = new DataFrame({ name: colA, value: colB, flag: colC }, { index });
+
+for (let i = 0; i < WARMUP; i++) {
+  toExcel(df);
+}
+
+const times: number[] = [];
+for (let i = 0; i < ITERATIONS; i++) {
+  const start = performance.now();
+  toExcel(df);
+  times.push(performance.now() - start);
+}
+
+const totalMs = times.reduce((a, b) => a + b, 0);
+const meanMs = totalMs / ITERATIONS;
+console.log(
+  JSON.stringify({
+    function: "to_excel",
+    mean_ms: Math.round(meanMs * 1000) / 1000,
+    iterations: ITERATIONS,
+    total_ms: Math.round(totalMs * 1000) / 1000,
+  }),
+);