refactor(db): typed query helpers, shared test FormData helper

Replace raw db.execute tuple casts with queryRows/rowsFrom/execResult/
affectedRows helpers from lib/db, drop redundant mysql2 casts on typed
query builders, and centralize per-test fakeForm into test/fake-form.
Update db mocks in tests so helpers resolve against mocked execute.

src/actions/admin-articles.ts

@@ -18,6 +18,7 @@ import {
 } from "@/lib/article-input";
 import {
 	db,
+	rowsFrom,
 	WebsiteArticleComments,
 	WebsiteArticleReactions,
 	WebsiteArticles,
@@ -128,11 +129,9 @@ export async function createArticle(
 					updatedAt: now,
 					publishedAt: fields.status === "published" ? now : null,
 				});
-				const [createdRows] = await tx.execute(
-					sql`SELECT CAST(LAST_INSERT_ID() AS CHAR) AS id`,
-				);
-				const articleId = (createdRows as unknown as Array<{ id: string }>)[0]
-					?.id;
+				const articleId = rowsFrom<{ id: string }>(
+					await tx.execute(sql`SELECT CAST(LAST_INSERT_ID() AS CHAR) AS id`),
+				)[0]?.id;
 				if (!articleId || !/^[1-9][0-9]*$/.test(articleId))
 					throw new Error("Article identity unavailable");
 				await enqueueEffect(tx, operationId, "news.refresh");