Allow configuring compile concurrency via CONCURRENCY env var

Defaults to 3 if not set.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sij411

packages/cli/scripts/pack.ts

@@ -56,7 +56,7 @@ async function pack(os: OS, arch: Arch): Promise<void> {
 const osFilter = Deno.env.get("OS")?.toLowerCase();
 const archFilter = Deno.env.get("ARCH")?.toLowerCase();
 
-const maxConcurrency = 3;
+const maxConcurrency = parseInt(Deno.env.get("CONCURRENCY") ?? "3");
 const tasks: Array<() => Promise<void>> = [];
 for (const osKey in triplets) {
   const os = osKey as OS;