feat(nodejs): expose connectNamespace for namespace-backed connections (#3383)

### Summary 

Adds a `connectNamespace(implName, properties, options?)` to the NodeJS
SDK`. Closes #3380.

### Testing
- pnpm test
- Ran smoke test

```
import { connectNamespace } from "lancedb"
import { tmpdir } from "os";
import { mkdtempSync } from "fs";
import { join } from "path";

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

// 1. Happy path: connect via the "dir" namespace impl, create + list a table.
console.log('Connecting via connectNamespace("dir", { root })...');
const db = await connectNamespace("dir", { root: dir });
console.log("  ✓ connected:", db.display());

console.log("Creating a table and listing it...");
await db.createTable("users", [
  { id: 1, name: "alice" },
  { id: 2, name: "bob" },
]);
console.log("  ✓ tableNames ->", await db.tableNames());

const table = await db.openTable("users");
console.log("  ✓ users.countRows ->", await table.countRows());

// 2. Storage options pass-through.
console.log("\nReconnecting with storageOptions (plumbing check)...");
const dbWithOpts = await connectNamespace(
  "dir",
  { root: dir },
  { storageOptions: { newTableDataStorageVersion: "stable" } },
);
console.log("  ✓ connected with storageOptions:", dbWithOpts.display());
await dbWithOpts.close();

// 3. Empty implName -> clear error.
console.log("\nCalling connectNamespace('', {}) (expect error)...");
try {
  await connectNamespace("", {});
  console.error("  UNEXPECTED: empty implName did not throw");
} catch (err) {
  console.log(`  ✓ Got expected error: ${err.message.split("\n")[0]}`);
}

// 4. Unknown impl -> error.
console.log("\nCalling connectNamespace('not-a-real-impl', {}) (expect error)...");
try {
  await connectNamespace("not-a-real-impl", {});
  console.error("  UNEXPECTED: unknown impl did not throw");
} catch (err) {
  console.log(`  ✓ Got expected error: ${err.message.split("\n")[0]}`);
}

// 5. Create a table inside a child namespace, then reconnect with a fresh
//    connectNamespace call and confirm the table is reachable via that
//    namespace path. (The dir+manifest impl keeps the namespace hierarchy in
//    a root manifest, so "scoping" happens via namespacePath args, not by
//    pointing root at a subdir.)
console.log("\nCreating a table inside a child namespace...");
const dir2 = mkdtempSync(join(tmpdir(), "lancedb-connect-namespace-smoke-"));
const writer = await connectNamespace("dir", {
  root: dir2,
  manifest_enabled: "true",
});
await writer.createNamespace(["analytics"]);
await writer.createTable(
  "orders",
  [
    { id: 1, total: 10 },
    { id: 2, total: 20 },
  ],
  ["analytics"],
);
console.log(
  "  ✓ writer sees tables under [analytics] ->",
  await writer.tableNames(["analytics"]),
);
await writer.close();

console.log("Reconnecting and reading the table via its namespace path...");
const reader = await connectNamespace("dir", {
  root: dir2,
  manifest_enabled: "true",
});
console.log(
  "  ✓ reader tableNames(['analytics']) ->",
  await reader.tableNames(["analytics"]),
);
const orders = await reader.openTable("orders", ["analytics"]);
console.log("  ✓ orders.countRows via reader ->", await orders.countRows());
await reader.close();

await db.close();
console.log("\nAll checks passed.");
```

```
Using temp dir: /var/folders/bj/hn6jv9c50y301d1nx0y8xmn00000gn/T/lancedb-connect-namespace-smoke-WByF1P

Connecting via connectNamespace("dir", { root })...
  ✓ connected: LanceNamespaceDatabase
Creating a table and listing it...
  ✓ tableNames -> [ 'users' ]
  ✓ users.countRows -> 2

Reconnecting with storageOptions (plumbing check)...
  ✓ connected with storageOptions: LanceNamespaceDatabase

Calling connectNamespace('', {}) (expect error)...
  ✓ Got expected error: implName must be a non-empty string

Calling connectNamespace('not-a-real-impl', {}) (expect error)...
  ✓ Got expected error: Invalid input, Failed to connect to namespace: Namespace { source: Unsupported { message: "Implementation 'not-a-real-impl' is not available. Supported: dir, rest" }, location: Location { file: "/Users/brendan/.cargo/git/checkouts/lance-8ddea23c38163eda/f693245/rust/lance-namespace-impls/src/connect.rs", line: 216, column: 14 } }

Creating a table inside a child namespace...
  ✓ writer sees tables under [analytics] -> [ 'orders' ]
Reconnecting and reading the table via its namespace path...
  ✓ reader tableNames(['analytics']) -> [ 'orders' ]
  ✓ orders.countRows via reader -> 2

All checks passed.
```

### Docs
- regenerated docs

docs/src/js/functions/connectNamespace.md

@@ -0,0 +1,131 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / connectNamespace
+
+# Function: connectNamespace()
+
+## connectNamespace(implName, config, options)
+
+```ts
+function connectNamespace(
+   implName,
+   config,
+   options?): Promise<Connection>
+```
+
+Connect to a LanceDB database through a namespace.
+
+Unlike [connect](connect.md), which routes by URI scheme (local path vs.
+`db://` cloud), `connectNamespace` always returns a namespace-backed
+connection. The `implName` selects the namespace implementation:
+
+- `"dir"` — directory namespace, configured with [DirNamespaceConfig](../interfaces/DirNamespaceConfig.md).
+- `"rest"` — remote REST catalog, configured with [RestNamespaceConfig](../interfaces/RestNamespaceConfig.md).
+- Any other string — full module path for a custom implementation,
+  configured with a free-form string-keyed `properties` map.
+
+### Parameters
+
+* **implName**: `"dir"`
+
+* **config**: [`DirNamespaceConfig`](../interfaces/DirNamespaceConfig.md)
+
+* **options?**: `Partial`&lt;[`ConnectNamespaceOptions`](../interfaces/ConnectNamespaceOptions.md)&gt;
+
+### Returns
+
+`Promise`&lt;[`Connection`](../classes/Connection.md)&gt;
+
+### Examples
+
+```ts
+const db = await connectNamespace("dir", { root: "/path/to/db" });
+await db.createTable("users", [{ id: 1 }]);
+```
+
+```ts
+const db = await connectNamespace("rest", {
+  uri: "https://catalog.example.com",
+  headers: { "x-api-key": process.env.CATALOG_KEY ?? "" },
+});
+```
+
+```ts
+const db = await connectNamespace("my.custom.Namespace", {
+  endpoint: "...",
+});
+```
+
+## connectNamespace(implName, config, options)
+
+```ts
+function connectNamespace(
+   implName,
+   config,
+   options?): Promise<Connection>
+```
+
+Connect through the built-in REST namespace.
+
+Configured with [RestNamespaceConfig](../interfaces/RestNamespaceConfig.md). See the function-level
+documentation above for the full surface, examples, and how this
+relates to [connect](connect.md).
+
+### Parameters
+
+* **implName**: `"rest"`
+
+* **config**: [`RestNamespaceConfig`](../interfaces/RestNamespaceConfig.md)
+
+* **options?**: `Partial`&lt;[`ConnectNamespaceOptions`](../interfaces/ConnectNamespaceOptions.md)&gt;
+
+### Returns
+
+`Promise`&lt;[`Connection`](../classes/Connection.md)&gt;
+
+### Example
+
+```ts
+const db = await connectNamespace("rest", {
+  uri: "https://catalog.example.com",
+  headers: { "x-api-key": process.env.CATALOG_KEY ?? "" },
+});
+```
+
+## connectNamespace(implName, properties, options)
+
+```ts
+function connectNamespace(
+   implName,
+   properties,
+   options?): Promise<Connection>
+```
+
+Connect through a custom namespace implementation by full module path,
+configured with a free-form string-keyed `properties` map. Use the
+typed overloads above for the built-in `"dir"` and `"rest"` impls.
+
+See the function-level documentation above for examples and how this
+relates to [connect](connect.md).
+
+### Parameters
+
+* **implName**: `string`
+
+* **properties**: `Record`&lt;`string`, `string`&gt;
+
+* **options?**: `Partial`&lt;[`ConnectNamespaceOptions`](../interfaces/ConnectNamespaceOptions.md)&gt;
+
+### Returns
+
+`Promise`&lt;[`Connection`](../classes/Connection.md)&gt;
+
+### Example
+
+```ts
+const db = await connectNamespace("my.custom.Namespace", {
+  endpoint: "...",
+});
+```

docs/src/js/globals.md

@@ -51,12 +51,14 @@
 - [ClientConfig](interfaces/ClientConfig.md)
 - [ColumnAlteration](interfaces/ColumnAlteration.md)
 - [CompactionStats](interfaces/CompactionStats.md)
+- [ConnectNamespaceOptions](interfaces/ConnectNamespaceOptions.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)
+- [DirNamespaceConfig](interfaces/DirNamespaceConfig.md)
 - [DropColumnsResult](interfaces/DropColumnsResult.md)
 - [DropNamespaceOptions](interfaces/DropNamespaceOptions.md)
 - [DropNamespaceResponse](interfaces/DropNamespaceResponse.md)
@@ -82,6 +84,7 @@
 - [OptimizeStats](interfaces/OptimizeStats.md)
 - [QueryExecutionOptions](interfaces/QueryExecutionOptions.md)
 - [RemovalStats](interfaces/RemovalStats.md)
+- [RestNamespaceConfig](interfaces/RestNamespaceConfig.md)
 - [RetryConfig](interfaces/RetryConfig.md)
 - [ShuffleOptions](interfaces/ShuffleOptions.md)
 - [SplitCalculatedOptions](interfaces/SplitCalculatedOptions.md)
@@ -114,6 +117,7 @@
 
 - [RecordBatchIterator](functions/RecordBatchIterator.md)
 - [connect](functions/connect.md)
+- [connectNamespace](functions/connectNamespace.md)
 - [makeArrowTable](functions/makeArrowTable.md)
 - [packBits](functions/packBits.md)
 - [permutationBuilder](functions/permutationBuilder.md)

docs/src/js/interfaces/ConnectNamespaceOptions.md

@@ -0,0 +1,54 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / ConnectNamespaceOptions
+
+# Interface: ConnectNamespaceOptions
+
+## Properties
+
+### namespaceClientProperties?
+
+```ts
+optional namespaceClientProperties: Record<string, string>;
+```
+
+Extra properties for the backing namespace client.
+
+***
+
+### readConsistencyInterval?
+
+```ts
+optional readConsistencyInterval: number;
+```
+
+The interval, in seconds, at which to check for updates to the table
+from other processes. If None, then consistency is not checked. For
+performance reasons, this is the default. For strong consistency, set
+this to zero seconds. Then every read will check for updates from other
+processes. As a compromise, you can set this to a non-zero value for
+eventual consistency.
+
+***
+
+### session?
+
+```ts
+optional session: Session;
+```
+
+The session to use for this connection. Holds shared caches and other
+session-specific state.
+
+***
+
+### storageOptions?
+
+```ts
+optional storageOptions: Record<string, string>;
+```
+
+Configuration for object storage. The available options are described
+at https://docs.lancedb.com/storage/

docs/src/js/interfaces/DirNamespaceConfig.md

@@ -0,0 +1,47 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / DirNamespaceConfig
+
+# Interface: DirNamespaceConfig
+
+Configuration for the built-in directory namespace (`"dir"`).
+
+The directory namespace stores tables under a single root path (local
+filesystem or object storage URI). See
+[https://docs.lancedb.com/namespaces](https://docs.lancedb.com/namespaces) for the documented surface;
+less-common knobs live under [DirNamespaceConfig.extraProperties](DirNamespaceConfig.md#extraproperties).
+
+## Properties
+
+### extraProperties?
+
+```ts
+optional extraProperties: Record<string, string>;
+```
+
+Additional raw properties passed verbatim to the namespace
+implementation (e.g. `storage.*`, `credential_vendor.*`). Typed
+fields above take precedence on key collision.
+
+***
+
+### manifestEnabled?
+
+```ts
+optional manifestEnabled: boolean;
+```
+
+Whether to maintain a namespace manifest at the root. Required for
+child namespaces. Defaults to true on the impl side.
+
+***
+
+### root
+
+```ts
+root: string;
+```
+
+Root path or URI containing the LanceDB tables.

docs/src/js/interfaces/RestNamespaceConfig.md

@@ -0,0 +1,47 @@
+[**@lancedb/lancedb**](../README.md) • **Docs**
+
+***
+
+[@lancedb/lancedb](../globals.md) / RestNamespaceConfig
+
+# Interface: RestNamespaceConfig
+
+Configuration for the built-in REST namespace (`"rest"`).
+
+The REST namespace talks to a remote catalog server over HTTP. See
+[https://docs.lancedb.com/namespaces](https://docs.lancedb.com/namespaces) for the documented surface;
+less-common knobs (TLS, metrics) live under
+[RestNamespaceConfig.extraProperties](RestNamespaceConfig.md#extraproperties).
+
+## Properties
+
+### extraProperties?
+
+```ts
+optional extraProperties: Record<string, string>;
+```
+
+Additional raw properties passed verbatim to the namespace
+implementation (e.g. `tls.*`, `ops_metrics_enabled`, `delimiter`).
+Typed fields above take precedence on key collision.
+
+***
+
+### headers?
+
+```ts
+optional headers: Record<string, string>;
+```
+
+HTTP headers forwarded with each request. Keys are passed through
+as-is (e.g. `"x-api-key"`, `"Authorization"`).
+
+***
+
+### uri
+
+```ts
+uri: string;
+```
+
+Catalog endpoint URL.