[runtime] harden versioned-routes server boot diagnostics

Why: CI failures were opaque when the test server failed to initialize with signing env inputs.
Contract impact: none

Author: GsCommand

runtime/tests/versioned-routes.test.mjs

@@ -2,7 +2,12 @@ import test from "node:test";
 import assert from "node:assert/strict";
 import { spawn } from "node:child_process";
 import net from "node:net";
-import { generateKeyPairSync, createHash } from "node:crypto";
+import { generateKeyPairSync } from "node:crypto";
+import { dirname, join } from "node:path";
+import { fileURLToPath } from "node:url";
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const SERVER_ENTRY = join(__dirname, "..", "..", "server.mjs");
 
 function freePort() {
   return new Promise((resolve, reject) => {
@@ -24,27 +29,50 @@ function makeKeys() {
   return {
     privatePemB64,
     publicRaw32B64: raw32.toString("base64"),
-    kid: createHash("sha256").update(raw32).digest("base64url").slice(0, 16),
   };
 }
 
 async function startServer(extraEnv) {
   const port = await freePort();
-  const proc = spawn(process.execPath, ["server.mjs"], {
-    cwd: process.cwd(),
+  const proc = spawn(process.execPath, [SERVER_ENTRY], {
     env: { ...process.env, HOST: "127.0.0.1", PORT: String(port), ...extraEnv },
     stdio: ["ignore", "pipe", "pipe"],
   });
+  let stdout = "";
+  let stderr = "";
+  proc.stdout.on("data", (chunk) => {
+    stdout += chunk.toString("utf8");
+  });
+  proc.stderr.on("data", (chunk) => {
+    stderr += chunk.toString("utf8");
+  });
 
   const base = `http://127.0.0.1:${port}`;
   for (let i = 0; i < 80; i++) {
+    if (proc.exitCode !== null) {
+      throw new Error(
+        [
+          `server exited before boot (exitCode=${proc.exitCode})`,
+          `entry=${SERVER_ENTRY}`,
+          `stdout:\n${stdout || "<empty>"}`,
+          `stderr:\n${stderr || "<empty>"}`,
+        ].join("\n")
+      );
+    }
     try {
       const r = await fetch(`${base}/health`);
       if (r.ok) return { proc, base };
     } catch {}
     await new Promise((r) => setTimeout(r, 100));
   }
-  throw new Error("server did not boot");
+  throw new Error(
+    [
+      `server did not boot after retries`,
+      `entry=${SERVER_ENTRY}`,
+      `stdout:\n${stdout || "<empty>"}`,
+      `stderr:\n${stderr || "<empty>"}`,
+    ].join("\n")
+  );
 }
 
 async function stop(proc) {