refactor(discord): dedupe guild listing

src/discord/guilds.ts

@@ -0,0 +1,29 @@
+import { fetchDiscord } from "./api.js";
+import { normalizeDiscordSlug } from "./monitor/allow-list.js";
+
+export type DiscordGuildSummary = {
+  id: string;
+  name: string;
+  slug: string;
+};
+
+export async function listGuilds(
+  token: string,
+  fetcher: typeof fetch,
+): Promise<DiscordGuildSummary[]> {
+  const raw = await fetchDiscord<Array<{ id?: string; name?: string }>>(
+    "/users/@me/guilds",
+    token,
+    fetcher,
+  );
+  return raw
+    .filter(
+      (guild): guild is { id: string; name: string } =>
+        typeof guild.id === "string" && typeof guild.name === "string",
+    )
+    .map((guild) => ({
+      id: guild.id,
+      name: guild.name,
+      slug: normalizeDiscordSlug(guild.name),
+    }));
+}