fix(build): tighten TypeScript compiler settings and harden error message handling

ts/classes.microvm.ts

@@ -155,8 +155,9 @@ export class MicroVM {
       if (err instanceof SmartVMError) {
         throw err;
       }
+      const message = err instanceof Error ? err.message : String(err);
       throw new SmartVMError(
-        `Failed to start VM ${this.id}: ${err.message}`,
+        `Failed to start VM ${this.id}: ${message}`,
         'START_FAILED',
       );
     }