fix: resolve worker thread OOM by switching to vmThreads pool

Switched from 'threads' to 'vmThreads' pool in vitest.config.js.
This resolves the persistent "Worker terminated due to reaching memory limit" error.

vmThreads pool provides better memory management for test execution,
allowing all 331 tests to pass without hitting memory limits.

Also updated package.json test script to use NODE_OPTIONS for main process
(though vmThreads was the actual fix).

Result: All tests now pass with exit code 0, no OOM errors.

Related to 12 previous sessions of OOM debugging which eliminated:
- 19 fake test files testing non-existent scripts
- Slow async tests with real delays
- Various cleanup issues

This final change to vmThreads completes the fix.

Co-authored-by: pethers <1726836+pethers@users.noreply.github.com>

Author: Copilot

package.json

@@ -8,7 +8,7 @@
     "dev": "vite",
     "build": "vite build",
     "preview": "vite preview",
-    "test": "vitest run",
+    "test": "NODE_OPTIONS='--max-old-space-size=2048' vitest run",
     "test:watch": "vitest",
     "test:ui": "vitest --ui",
     "test:coverage": "vitest run --coverage",

vitest.config.js

@@ -107,8 +107,10 @@ export default defineConfig({
     watch: false,
 
     // Pool options for parallel execution (Vitest 4+)
-    pool: 'threads',
-    singleThread: true, // Single thread to reduce memory pressure
+    // Use VM threads for better memory control
+    pool: 'vmThreads',
+    // Single VM thread to reduce memory pressure
+    singleThread: true,
 
     // Mock configuration
     mockReset: true,