Fix: Raise exceptions from add() in JS (#486)

For example, if you try to add the same key, it aborts.

```
terminate called after throwing an instance of 'std::runtime_error'
  what():  Duplicate keys not allowed in high-level wrappers
Aborted (core dumped)
```

Improved error handling to throw JavaScript exceptions.

javascript/lib.cpp

@@ -20,6 +20,8 @@
 using namespace unum::usearch;
 using namespace unum;
 
+using add_result_t = typename index_dense_t::add_result_t;
+
 class CompiledIndex : public Napi::ObjectWrap<CompiledIndex> {
   public:
     static Napi::Object Init(Napi::Env env, Napi::Object exports);
@@ -161,7 +163,10 @@ void CompiledIndex::Add(Napi::CallbackInfo const& ctx) {
     auto run_parallel = [&](auto vectors) {
         executor_stl_t executor;
         executor.fixed(tasks, [&](std::size_t /*thread_idx*/, std::size_t task_idx) {
-            native_->add(static_cast<default_key_t>(keys[task_idx]), vectors + task_idx * native_->dimensions());
+            add_result_t result = native_->add(static_cast<default_key_t>(keys[task_idx]),
+                                               vectors + task_idx * native_->dimensions());
+            if (!result)
+                Napi::Error::New(ctx.Env(), result.error.release()).ThrowAsJavaScriptException();
         });
     };
 

javascript/usearch.test.js

@@ -104,3 +104,21 @@ test('Operations with invalid values', () => {
         }
     );
 });
+
+test('Invalid operations', async (t) => {
+    await t.test('Add the same keys', () => {
+        const index = new usearch.Index({
+            metric: "l2sq",
+            connectivity: 16,
+            dimensions: 3,
+        });
+        index.add(42n, new Float32Array([0.2, 0.6, 0.4]));
+        assert.throws(
+            () => index.add(42n, new Float32Array([0.2, 0.6, 0.4])),
+            {
+                name: 'Error',
+                message: 'Duplicate keys not allowed in high-level wrappers'
+            }
+        );
+    });
+});