fix: add DurableObject import from cloudflare:workers to all DO classes

Without the explicit import, tsc sees the global DurableObject interface
(not extendable) instead of the abstract class from cloudflare:workers.

Author: teamchong

src/fragment-do.ts

@@ -1,3 +1,4 @@
+import { DurableObject } from "cloudflare:workers";
 import type { Env, TableMeta, QueryResult, Row } from "./types.js";
 import type { QueryDescriptor } from "./client.js";
 import { canSkipPage } from "./decode.js";

src/master-do.ts

@@ -1,3 +1,4 @@
+import { DurableObject } from "cloudflare:workers";
 import type { ColumnMeta, Env, Footer, TableMeta, DatasetMeta, AppendResult } from "./types.js";
 import { parseFooter, parseColumnMetaFromProtobuf, FOOTER_SIZE } from "./footer.js";
 import { parseManifest } from "./manifest.js";

src/query-do.ts

@@ -1,3 +1,4 @@
+import { DurableObject } from "cloudflare:workers";
 import type { ColumnMeta, DataType, Env, ExplainResult, Footer, Row, TableMeta, DatasetMeta, IcebergDatasetMeta, QueryResult } from "./types.js";
 import type { QueryDescriptor } from "./client.js";
 import { parseFooter, parseColumnMetaFromProtobuf } from "./footer.js";