fix(ci): harden test determinism and dependencies

scripts/prepare.mjs

@@ -0,0 +1,17 @@
+import { spawnSync } from "node:child_process";
+import { existsSync } from "node:fs";
+
+if (!existsSync(".git")) {
+  console.log("Skipping Lefthook install: Git metadata is absent");
+} else {
+  const result = spawnSync("lefthook", ["install", "--force"], {
+    stdio: "inherit",
+    shell: process.platform === "win32",
+  });
+  if (result.error) {
+    console.error(`Failed to run Lefthook: ${result.error.message}`);
+    process.exitCode = 1;
+  } else {
+    process.exitCode = result.status ?? 1;
+  }
+}