feat(nodejs): add namespace management methods on Connection (#3371)

### Summary

Closes #3363 

Adds the four namespace management methods to the NodeJS `Connection`,
bringing parity with the Rust core and Python bindings:

- `listNamespaces(parent?, options?)`
- `createNamespace(namespacePath, options?)`
- `dropNamespace(namespacePath, options?)`
- `describeNamespace(namespacePath)`

### Test plan
- npm test
- Ran a smoke test script

```typescript
import { connect } from '<lancePath>'
import { tmpdir } from "os";
import { mkdtempSync } from "fs";
import { join } from "path";

const dir = mkdtempSync(join(tmpdir(), "lancedb-smoke-"));
console.log(`Using temp dir: ${dir}\n`);

const db = await connect(dir, {
  namespaceClientProperties: { manifest_enabled: "true" },
});

console.log("Creating namespaces...");
await db.createNamespace(["analytics"]);
await db.createNamespace(["analytics", "sales"], {
  properties: { owner: "brendan", purpose: "smoke-test" },
});
await db.createNamespace(["marketing"]);

const root = await db.listNamespaces();
console.log("Root namespaces:", root.namespaces);

const children = await db.listNamespaces(["analytics"]);
console.log("Children of 'analytics':", children.namespaces);

const descWithProps = await db.describeNamespace(["analytics", "sales"]);
console.log("Describe analytics/sales (with properties):", descWithProps);

const descNoProps = await db.describeNamespace(["analytics"]);
console.log("Describe analytics (no properties):", descNoProps);

console.log("Describing a non-existent namespace (expect error)...");
try {
  await db.describeNamespace(["does-not-exist"]);
  console.error("  UNEXPECTED: describe succeeded for non-existent namespace");
} catch (err) {
  console.log(`  ✓ Got expected error: ${err.message.split("\n")[0]}`);
}

await db.dropNamespace(["marketing"]);
const afterDrop = await db.listNamespaces();
console.log("Root after dropping marketing:", afterDrop.namespaces);

await db.close();
console.log("\nAll operations completed successfully.");
```

```
Using temp dir: /var/folders/bj/hn6jv9c50y301d1nx0y8xmn00000gn/T/lancedb-smoke-MUC5NI

Creating namespaces...
Root namespaces: [ 'analytics', 'marketing' ]
Children of 'analytics': [ 'sales' ]
Describe analytics/sales (with properties): { properties: { purpose: 'smoke-test', owner: 'brendan' } }
Describe analytics (no properties): {}
Describing a non-existent namespace (expect error)...
  ✓ Got expected error: lance error: Namespace error: Namespace not found: does-not-exist, rust/lance-namespace-impls/src/dir/manifest.rs:2495:14  Caused by: Namespace error: Namespace not found: does-not-exist, rust/lance-namespace-impls/src/dir/manifest.rs:2495:14    Caused by: Namespace not found: does-not-exist
Root after dropping marketing: [ 'analytics' ]

All operations completed successfully.
```

### Documentation
- regenerated docs

docs/src/js/globals.md

@@ -52,9 +52,14 @@
 - [ColumnAlteration](interfaces/ColumnAlteration.md)
 - [CompactionStats](interfaces/CompactionStats.md)
 - [ConnectionOptions](interfaces/ConnectionOptions.md)
+- [CreateNamespaceOptions](interfaces/CreateNamespaceOptions.md)
+- [CreateNamespaceResponse](interfaces/CreateNamespaceResponse.md)
 - [CreateTableOptions](interfaces/CreateTableOptions.md)
 - [DeleteResult](interfaces/DeleteResult.md)
+- [DescribeNamespaceResponse](interfaces/DescribeNamespaceResponse.md)
 - [DropColumnsResult](interfaces/DropColumnsResult.md)
+- [DropNamespaceOptions](interfaces/DropNamespaceOptions.md)
+- [DropNamespaceResponse](interfaces/DropNamespaceResponse.md)
 - [ExecutableQuery](interfaces/ExecutableQuery.md)
 - [FragmentStatistics](interfaces/FragmentStatistics.md)
 - [FragmentSummaryStats](interfaces/FragmentSummaryStats.md)
@@ -69,6 +74,8 @@
 - [IvfFlatOptions](interfaces/IvfFlatOptions.md)
 - [IvfPqOptions](interfaces/IvfPqOptions.md)
 - [IvfRqOptions](interfaces/IvfRqOptions.md)
+- [ListNamespacesOptions](interfaces/ListNamespacesOptions.md)
+- [ListNamespacesResponse](interfaces/ListNamespacesResponse.md)
 - [MergeResult](interfaces/MergeResult.md)
 - [OpenTableOptions](interfaces/OpenTableOptions.md)
 - [OptimizeOptions](interfaces/OptimizeOptions.md)