fix: correct Node.js version references from 24 to 22 in comments and code

Fixed confusing messaging where comments mentioned Node 24 while actual requirement is Node 22:

- environment.ts: Fixed areWorkerThreadsAvailableSync() to check for >= 22 instead of >= 24
- workerUtils.ts: Updated comments to reference Node.js 22 LTS instead of 24
- embedding.ts: Updated ONNX threading comment to reference Node.js 22 LTS

Why Node 22 not Node 24:
- ONNX Runtime has stability issues in Node 24 (V8 HandleScope crashes)
- Node 22 LTS provides maximum stability with our embedding model
- These stale Node 24 references were causing user confusion

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/utils/environment.ts

@@ -66,8 +66,8 @@ export async function areWorkerThreadsAvailable(): Promise<boolean> {
 export function areWorkerThreadsAvailableSync(): boolean {
   if (!isNode()) return false
 
-  // In Node.js 24.4.0+, worker_threads is always available
-  return parseInt(process.versions.node.split('.')[0]) >= 24
+  // In Node.js 22+, worker_threads is always available
+  return parseInt(process.versions.node.split('.')[0]) >= 22
 }
 
 /**