Migrate CLI E2E tests to Node.js 26

Run the CLI subprocess suites and benchmark tools as native TypeScript with
node:test, and move them under test/e2e-cli.

Update CI and Compose runners, run local smoke tests on Linux, macOS, and
Windows, and collect source-mapped CLI coverage with c8.

test/e2e-cli/helpers/benchmarkVerification.ts

@@ -0,0 +1,74 @@
+import { createHash } from "node:crypto";
+import { readFile } from "node:fs/promises";
+import type { DatasetEntry } from "./dataset.ts";
+
+export type BenchmarkVerificationMode = "all" | "sample";
+
+export type BenchmarkVerificationResult = {
+    verificationMode: BenchmarkVerificationMode;
+    verifiedFiles: number;
+    verificationComplete: boolean;
+    datasetDigestSha256: string;
+};
+
+function sha256(bytes: Uint8Array): string {
+    return createHash("sha256").update(bytes).digest("hex");
+}
+
+export function parseBenchmarkVerificationMode(
+    raw: string | undefined,
+    fallback: BenchmarkVerificationMode = "sample",
+): BenchmarkVerificationMode {
+    const value = raw?.trim().toLowerCase();
+    if (!value) return fallback;
+    if (value === "all" || value === "sample") return value;
+    throw new Error(`BENCH_VERIFY_MODE must be 'all' or 'sample', got '${raw}'`);
+}
+
+export function selectVerificationEntries(
+    entries: DatasetEntry[],
+    mode: BenchmarkVerificationMode,
+): DatasetEntry[] {
+    if (mode === "all" || entries.length === 0) return [...entries];
+
+    const md = entries.find((entry) => entry.kind === "md");
+    const bin = entries.find((entry) => entry.kind === "bin");
+    const middle = entries[Math.floor(entries.length / 2)];
+    const last = entries[entries.length - 1];
+    const selected = new Map<string, DatasetEntry>();
+    for (const entry of [md, bin, middle, last]) {
+        if (entry) selected.set(entry.relativePath, entry);
+    }
+    return [...selected.values()];
+}
+
+export async function computeDatasetDigestSha256(
+    entries: DatasetEntry[],
+): Promise<string> {
+    const manifest: string[] = [];
+    for (const entry of entries) {
+        const contentDigest = sha256(await readFile(entry.absolutePath));
+        manifest.push(
+            `${entry.kind}\t${entry.relativePath}\t${entry.size}\t${contentDigest}`,
+        );
+    }
+    return sha256(new TextEncoder().encode(manifest.join("\n")));
+}
+
+export async function verifyBenchmarkDataset(
+    entries: DatasetEntry[],
+    mode: BenchmarkVerificationMode,
+    verifyEntry: (entry: DatasetEntry) => Promise<void>,
+): Promise<BenchmarkVerificationResult> {
+    const selected = selectVerificationEntries(entries, mode);
+    for (const entry of selected) {
+        await verifyEntry(entry);
+    }
+
+    return {
+        verificationMode: mode,
+        verifiedFiles: selected.length,
+        verificationComplete: selected.length === entries.length,
+        datasetDigestSha256: await computeDatasetDigestSha256(entries),
+    };
+}