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

nodejs/src/connection.rs

@@ -8,11 +8,12 @@ use lancedb::database::{CreateTableMode, Database};
 use napi::bindgen_prelude::*;
 use napi_derive::*;
 
+use crate::ConnectNamespaceOptions;
 use crate::ConnectionOptions;
 use crate::error::NapiErrorExt;
 use crate::header::JsHeaderProvider;
 use crate::table::Table;
-use lancedb::connection::{ConnectBuilder, Connection as LanceDBConnection};
+use lancedb::connection::{ConnectBuilder, Connection as LanceDBConnection, connect_namespace};
 
 use lance_namespace::models::{
     CreateNamespaceRequest, DescribeNamespaceRequest, DropNamespaceRequest, ListNamespacesRequest,
@@ -132,6 +133,39 @@ impl Connection {
         Ok(Self::inner_new(builder.execute().await.default_error()?))
     }
 
+    /// Create a new Connection instance backed by a namespace implementation.
+    #[napi(factory)]
+    pub async fn new_with_namespace(
+        impl_name: String,
+        properties: HashMap<String, String>,
+        options: ConnectNamespaceOptions,
+    ) -> napi::Result<Self> {
+        if impl_name.is_empty() {
+            return Err(napi::Error::from_reason(
+                "implName must be a non-empty string",
+            ));
+        }
+
+        let mut builder = connect_namespace(&impl_name, properties);
+        if let Some(interval) = options.read_consistency_interval {
+            builder =
+                builder.read_consistency_interval(std::time::Duration::from_secs_f64(interval));
+        }
+        if let Some(storage_options) = options.storage_options {
+            for (key, value) in storage_options {
+                builder = builder.storage_option(key, value);
+            }
+        }
+        if let Some(namespace_client_properties) = options.namespace_client_properties {
+            builder = builder.namespace_client_properties(namespace_client_properties);
+        }
+        if let Some(session) = options.session {
+            builder = builder.session(session.inner.clone());
+        }
+
+        Ok(Self::inner_new(builder.execute().await.default_error()?))
+    }
+
     #[napi]
     pub fn display(&self) -> napi::Result<String> {
         Ok(self.get_inner()?.to_string())

nodejs/src/lib.rs

@@ -67,6 +67,26 @@ pub struct OpenTableOptions {
     pub storage_options: Option<HashMap<String, String>>,
 }
 
+#[napi(object)]
+#[derive(Debug)]
+pub struct ConnectNamespaceOptions {
+    /// 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.
+    pub read_consistency_interval: Option<f64>,
+    /// Configuration for object storage. The available options are described
+    /// at https://docs.lancedb.com/storage/
+    pub storage_options: Option<HashMap<String, String>>,
+    /// Extra properties for the backing namespace client.
+    pub namespace_client_properties: Option<HashMap<String, String>>,
+    /// The session to use for this connection. Holds shared caches and other
+    /// session-specific state.
+    pub session: Option<session::Session>,
+}
+
 #[napi_derive::module_init]
 fn init() {
     let env = Env::new()