[types] Include re-exported types in top-level folders again.

This allows TypeScript to pick up the types without having to author `tsconfig.json`, particularly in VS Code.

I want to get rid of this as soon as possible, as using anything other than the `"exports" field in `package.json` is an anti-pattern. But this is going to provide a much better experience in the meantime.

Makefile

@@ -31,6 +31,7 @@ default:
 # an error).
 .PHONY: build
 build: clean build-lib build-bin build-sites
+	${BUN_RUN} script/build/lib/clean-types.ts
 .PHONY: build-lib
 build-lib: build-lib-js build-lib-types
 .PHONY: build-lib-js

script/build/lib/build-lib-types.ts

@@ -1,4 +1,5 @@
-import { rename } from "fs/promises";
+import { mkdir, rename, writeFile } from "node:fs/promises";
+import { join } from "node:path";
 import { spawnPromise } from "../../lib/execPromise";
 import { packageNames } from "../common/package-info";
 
@@ -35,3 +36,25 @@ await spawnPromise("npx", [
   "--out-dir",
   "dist/lib/cubing",
 ]);
+
+const TYPESCRIPT_DECLARATION_INDEX = "index.d.ts";
+
+// TODO: remove this once TypeScript resolves types from the `package.json` exports out of the box.
+for (const packageName of packageNames) {
+  await mkdir(packageName);
+  const indexFileName = join(packageName, TYPESCRIPT_DECLARATION_INDEX);
+  await writeFile(
+    indexFileName,
+    `export type * from ${JSON.stringify(
+      join(
+        "..",
+        "dist",
+        "lib",
+        "cubing",
+        packageName,
+        TYPESCRIPT_DECLARATION_INDEX,
+      ),
+    )};`,
+    "utf-8",
+  );
+}

script/build/lib/clean-types.ts

@@ -0,0 +1,11 @@
+import { rm, rmdir } from "node:fs/promises";
+import { join } from "node:path";
+import { packageNames } from "../common/package-info";
+
+const TYPESCRIPT_DECLARATION_INDEX = "index.d.ts";
+
+for (const packageName of packageNames) {
+  const indexFileName = join(packageName, TYPESCRIPT_DECLARATION_INDEX);
+  await rm(indexFileName);
+  await rmdir(packageName);
+}