feat: add use_index parameter to merge insert operations (#2674)

## Summary

Exposes `use_index` Merge Insert parameter, which was created upstream
in https://github.com/lancedb/lance/pull/4688.

## API Examples

### Python
```python
# Force table scan
table.merge_insert(["id"]) \
    .when_not_matched_insert_all() \
    .use_index(False) \
    .execute(data)
```

### Node.js/TypeScript
```typescript
// Force table scan  
await table.mergeInsert("id")
    .whenNotMatchedInsertAll()
    .useIndex(false)
    .execute(data);
```

### Rust
```rust
// Force table scan
let mut builder = table.merge_insert(&["id"]);
builder.when_not_matched_insert_all()
       .use_index(false);
builder.execute(data).await?;
```

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

Co-authored-by: Claude <noreply@anthropic.com>

nodejs/src/merge.rs

@@ -43,6 +43,13 @@ impl NativeMergeInsertBuilder {
         self.inner.timeout(Duration::from_millis(timeout as u64));
     }
 
+    #[napi]
+    pub fn use_index(&self, use_index: bool) -> Self {
+        let mut this = self.clone();
+        this.inner.use_index(use_index);
+        this
+    }
+
     #[napi(catch_unwind)]
     pub async fn execute(&self, buf: Buffer) -> napi::Result<MergeResult> {
         let data = ipc_file_to_batches(buf.to_vec())