Drop Deno from the agents and spawn child processes directly

tests/entrypoints.test.ts

@@ -1,10 +1,9 @@
+import { spawnSync } from "node:child_process";
 import process from "node:process";
 import { fileURLToPath } from "node:url";
 
 import { expect, test } from "vite-plus/test";
 
-import { output } from "../src/command.ts";
-
 // Each phase runs as `node src/<phase>.ts` with no build step. Node loads the
 // whole import graph, stripping types, before the phase reads its first
 // variable, so failing on that variable proves every module loads.
@@ -14,14 +13,13 @@ const PHASES: [phase: string, firstVariable: string][] = [
   ["post", "BOT_AGENTS_MANIFEST"],
 ];
 
-test.each(PHASES)("Node loads the %s phase", async (phase, firstVariable) => {
+test.each(PHASES)("Node loads the %s phase", (phase, firstVariable) => {
   const path = fileURLToPath(new URL(`../src/${phase}.ts`, import.meta.url));
-  const result = await output(process.execPath, {
-    args: [path],
+  const result = spawnSync(process.execPath, [path], {
     env: { PATH: process.env.PATH ?? "" },
-    clearEnv: true,
-    stdin: "null",
+    stdio: ["ignore", "pipe", "pipe"],
+    encoding: "utf8",
   });
-  expect(result.success).toBe(false);
-  expect(new TextDecoder().decode(result.stderr)).toContain(`${firstVariable} is not set`);
+  expect(result.status).not.toBe(0);
+  expect(result.stderr).toContain(`${firstVariable} is not set`);
 });