fix(build): Guard import.meta usage for CJS Smithery builds

Smithery capability scanning runs a CJS bundle in CI. Accessing fileURLToPath(importMetaUrl) without a guard can throw when import.meta is present but does not include a usable url, which broke the build-and-test job.

Guard the import-meta candidate so package-root discovery still works via process.cwd() and argv fallbacks in CJS environments.

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

Author: cameroncooke

src/core/resource-root.ts

@@ -21,7 +21,10 @@ function findPackageRootFrom(startDir: string): string | null {
 
 export function getPackageRoot(): string {
   const candidates: string[] = [];
-  candidates.push(path.dirname(fileURLToPath(import.meta.url)));
+  const importMetaUrl = typeof import.meta.url === 'string' ? import.meta.url : null;
+  if (importMetaUrl) {
+    candidates.push(path.dirname(fileURLToPath(importMetaUrl)));
+  }
   candidates.push(process.cwd());
   const entry = process.argv[1];
   if (entry) {