fix(tests): limit parallelism

Author: vados-cosmonic

test/vitest.ts

@@ -1,3 +1,5 @@
+import { availableParallelism } from 'node:os';
+
 import { defineConfig } from 'vitest/config';
 
 const DEFAULT_TIMEOUT_MS = 120_000;
@@ -10,6 +12,7 @@ export default defineConfig({
   test: {
     reporters: REPORTERS,
     disableConsoleIntercept: true,
+    maxConcurrency: Math.max(availableParallelism() / 2, 5),
     printConsoleTrace: true,
     passWithNoTests: false,
     include: ['test/**/*.js'],