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/interfaces/CreateNamespaceOptions.md

@@ -0,0 +1,27 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / CreateNamespaceOptions
+
+# Interface: CreateNamespaceOptions
+
+## Properties
+
+### mode?
+
+```ts
+optional mode: "overwrite" | "create" | "exist_ok";
+```
+
+Creation mode.
+
+***
+
+### properties?
+
+```ts
+optional properties: Record<string, string>;
+```
+
+Properties to set on the new namespace.

docs/src/js/interfaces/CreateNamespaceResponse.md

@@ -0,0 +1,23 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / CreateNamespaceResponse
+
+# Interface: CreateNamespaceResponse
+
+## Properties
+
+### properties?
+
+```ts
+optional properties: Record<string, string>;
+```
+
+***
+
+### transactionId?
+
+```ts
+optional transactionId: string;
+```

docs/src/js/interfaces/DescribeNamespaceResponse.md

@@ -0,0 +1,15 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / DescribeNamespaceResponse
+
+# Interface: DescribeNamespaceResponse
+
+## Properties
+
+### properties?
+
+```ts
+optional properties: Record<string, string>;
+```

docs/src/js/interfaces/DropNamespaceOptions.md

@@ -0,0 +1,27 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / DropNamespaceOptions
+
+# Interface: DropNamespaceOptions
+
+## Properties
+
+### behavior?
+
+```ts
+optional behavior: "restrict" | "cascade";
+```
+
+Refuse to drop if non-empty (restrict) or drop recursively (cascade).
+
+***
+
+### mode?
+
+```ts
+optional mode: "fail" | "skip";
+```
+
+Whether to skip if the namespace doesn't exist, or fail.

docs/src/js/interfaces/DropNamespaceResponse.md

@@ -0,0 +1,23 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / DropNamespaceResponse
+
+# Interface: DropNamespaceResponse
+
+## Properties
+
+### properties?
+
+```ts
+optional properties: Record<string, string>;
+```
+
+***
+
+### transactionId?
+
+```ts
+optional transactionId: string[];
+```

docs/src/js/interfaces/ListNamespacesOptions.md

@@ -0,0 +1,27 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / ListNamespacesOptions
+
+# Interface: ListNamespacesOptions
+
+## Properties
+
+### limit?
+
+```ts
+optional limit: number;
+```
+
+An optional limit to the number of results to return.
+
+***
+
+### pageToken?
+
+```ts
+optional pageToken: string;
+```
+
+Token from a previous response for pagination.

docs/src/js/interfaces/ListNamespacesResponse.md

@@ -0,0 +1,23 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / ListNamespacesResponse
+
+# Interface: ListNamespacesResponse
+
+## Properties
+
+### namespaces
+
+```ts
+namespaces: string[];
+```
+
+***
+
+### pageToken?
+
+```ts
+optional pageToken: string;
+```