feat(sea): execute statements asynchronously (submit + poll) for Thrift parity

The SEA backend's executeStatement used the blocking napi executeStatement
(kernel polled to terminal internally), so SeaOperationBackend.status()
synthesized a constant FINISHED and a long-running query could not be
cancelled from JS until it returned. The Thrift backend always runs
async (runAsync: true): it submits, gets a pending operation handle, and
polls getOperationStatus to terminal during waitUntilReady.

This brings the SEA path to the same model:

- SeaSessionBackend.executeStatement now calls the napi submitStatement
  (kernel wait_timeout=0s), receiving a pending AsyncStatement handle.
  Metadata methods keep the blocking statement path (already terminal).
- SeaOperationBackend supports both shapes: for the async path,
  waitUntilReady() polls status() to terminal (firing the progress
  callback each tick, like the Thrift getOperationStatus loop), then
  materialises the result stream via awaitResult(); status() reports the
  real Pending/Running/Succeeded/Failed state; a Failed statement surfaces
  the kernel's typed SQL-error envelope via awaitResult()'s rejection.
- The JS-side poll loop (not a single blocking awaitResult) keeps cancel()
  responsive: the kernel AsyncStatement serialises its methods behind one
  mutex, so a single in-flight awaitResult() would queue cancel() behind
  it for the whole query; polling status() releases the mutex between ticks.
- SeaNativeLoader gains the typed async surface (submitStatement,
  SeaNativeAsyncStatement, SeaNativeAsyncResultHandle, SeaNativeStatementStatus).

Co-authored-by: Isaac
Signed-off-by: Madhavendra Rathore <madhavendra.rathore@databricks.com>

Author: msrathore-db

lib/sea/SeaNativeLoader.ts

@@ -64,6 +64,49 @@ export interface SeaNativeStatement {
   close(): Promise<void>;
 }
 
+/**
+ * Server-side execution status returned by `AsyncStatement.status()`.
+ * Mirrors the kernel `StatementStatus` enum collapsed to its variant
+ * name. `'Unknown'` is the forward-compat arm for kernel variants the
+ * binding doesn't recognise.
+ */
+export type SeaNativeStatementStatus =
+  | 'Pending'
+  | 'Running'
+  | 'Succeeded'
+  | 'Failed'
+  | 'Cancelled'
+  | 'Closed'
+  | 'Unknown';
+
+/**
+ * Typed surface for the opaque napi `AsyncResultHandle`. Returned by
+ * `AsyncStatement.awaitResult()`; same fetch-side surface as
+ * `SeaNativeStatement` but without `cancel()` / `close()` (the parent
+ * `AsyncStatement` owns server-side lifecycle).
+ */
+export interface SeaNativeAsyncResultHandle {
+  readonly statementId: string;
+  fetchNextBatch(): Promise<SeaArrowBatch | null>;
+  schema(): Promise<SeaArrowSchema>;
+}
+
+/**
+ * Typed surface for the opaque napi `AsyncStatement`. Returned by
+ * `Connection.submitStatement(...)`. The kernel submits with
+ * `wait_timeout=0s`, so the server returns a `statementId` while the
+ * query is still Pending/Running; JS drives polling via `status()`
+ * and materialises results with `awaitResult()`. This is the
+ * async-execution path the Thrift backend always uses (`runAsync`).
+ */
+export interface SeaNativeAsyncStatement {
+  readonly statementId: string;
+  status(): Promise<SeaNativeStatementStatus>;
+  awaitResult(): Promise<SeaNativeAsyncResultHandle>;
+  cancel(): Promise<void>;
+  close(): Promise<void>;
+}
+
 /**
  * Typed surface for the opaque napi `Connection` handle. Signatures
  * match `native/sea/index.d.ts` exactly as generated by napi-rs from
@@ -118,6 +161,18 @@ export interface SeaNativeConnection {
    */
   executeStatement(sql: string, options?: SeaNativeExecuteOptions): Promise<SeaNativeStatement>;
 
+  /**
+   * Submit a SQL statement asynchronously and return an
+   * `AsyncStatement` handle without blocking until the query
+   * finishes. The kernel sends `wait_timeout=0s`, so the server
+   * responds as soon as it has a `statementId` (Pending/Running);
+   * drive polling via the handle's `status()` / `awaitResult()`.
+   * Same option semantics as `executeStatement`; only the
+   * pending-vs-blocking return contract differs. This is the
+   * async-execution path the Thrift backend always uses.
+   */
+  submitStatement(sql: string, options?: SeaNativeExecuteOptions): Promise<SeaNativeAsyncStatement>;
+
   // ── Metadata methods ──────────────────────────────────────────────────
   /** All catalogs visible to the session. */
   listCatalogs(): Promise<SeaNativeStatement>;