feat: add X parent post article extraction and validation

src/lib/article.js

@@ -0,0 +1,37 @@
+"use strict";
+
+function normalizeWhitespace(text) {
+  return text.replace(/\s+/g, " ").trim();
+}
+
+function extractArticleFromParent(parentPost) {
+  if (!parentPost || typeof parentPost !== "object") {
+    return { ok: false, error: "parent_post_missing" };
+  }
+
+  const article = parentPost.article;
+  if (!article || typeof article.body !== "string") {
+    return { ok: false, error: "not_article" };
+  }
+
+  const rawBody = normalizeWhitespace(article.body);
+  if (!rawBody) {
+    return { ok: false, error: "empty_article" };
+  }
+
+  return {
+    ok: true,
+    article: {
+      xArticleId: article.id || null,
+      parentPostId: parentPost.id,
+      authorId: parentPost.authorId || null,
+      title: article.title || "Untitled",
+      content: rawBody,
+      charCount: rawBody.length,
+    },
+  };
+}
+
+module.exports = {
+  extractArticleFromParent,
+};