feat(node): add blob v2 fetch and field helpers (#4155)

this PR blob v2 field helpers and reads to the Node SDK.

`blob()` marks a field as blob v2 and lets you set the storage
thresholds. Inputs can be bytes, a URI, or a data/uri struct.

Queries return descriptors. `fetchBlobs()` reads the bytes by row ID,
and `fetchBlobFiles()` gives you lazy handles for full or range reads.
`blobColumns()` lists the blob fields, including nested ones.

Fetch uses the table’s current checkout. It preserves order, duplicates,
and nulls. Holding row IDs across compaction still requires stable row
IDs.

```javascript
const db = await connect("./data");
const video = await readFile("clip.mp4");
const table = await db.createTable(
  "videos",
  [{ id: 1n, video }],
  {
    schema: new Schema([
      new Field("id", new Int64()),
      blob("video"),
    ]),
  },
);
const rows = await table.query().select(["id"]).withRowId().toArray();
const rowIds = rows.map((row) => row._rowid as bigint);
const bytes = await table.fetchBlobs("video", rowIds);
const [handle] = await table.fetchBlobFiles("video", rowIds);
const header = await handle!.readRange(0n, 65536n);

```

### Testing

- cover input validation, thresholds, nested fields, fetch ordering,
nulls, and range reads.

nodejs/src/table.rs

@@ -15,6 +15,7 @@ use napi::bindgen_prelude::*;
 use napi::threadsafe_function::{ThreadsafeFunction, ThreadsafeFunctionCallMode};
 use napi_derive::napi;
 
+use crate::blob::{BlobFile, copy_blob_buffers, parse_row_ids};
 use crate::error::NapiErrorExt;
 use crate::index::Index;
 use crate::merge::NativeMergeInsertBuilder;
@@ -329,6 +330,44 @@ impl Table {
         ))
     }
 
+    #[napi(catch_unwind)]
+    pub async fn blob_columns(&self) -> napi::Result<Vec<String>> {
+        self.inner_ref()?.blob_columns().await.default_error()
+    }
+
+    #[napi(catch_unwind)]
+    pub async fn fetch_blobs(
+        &self,
+        column: String,
+        row_ids: Vec<BigInt>,
+    ) -> napi::Result<Vec<Option<Buffer>>> {
+        let row_ids = parse_row_ids(row_ids)?;
+        let array = self
+            .inner_ref()?
+            .fetch_blobs(column.as_str(), &row_ids)
+            .await
+            .default_error()?;
+        Ok(copy_blob_buffers(array))
+    }
+
+    #[napi(catch_unwind)]
+    pub async fn fetch_blob_files(
+        &self,
+        column: String,
+        row_ids: Vec<BigInt>,
+    ) -> napi::Result<Vec<Option<BlobFile>>> {
+        let row_ids = parse_row_ids(row_ids)?;
+        let files = self
+            .inner_ref()?
+            .fetch_blob_files(column.as_str(), &row_ids)
+            .await
+            .default_error()?;
+        Ok(files
+            .into_iter()
+            .map(|file| file.map(BlobFile::new))
+            .collect())
+    }
+
     #[napi(catch_unwind)]
     pub fn vector_search(&self, vector: Float32Array) -> napi::Result<VectorQuery> {
         self.query()?.nearest_to(vector)