feat(core): custom field definitions and value validation

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/core/test/user-layer-fixtures.ts

@@ -0,0 +1,65 @@
+import type { Db } from "@sttracker/db/db";
+import { newId, nowIso } from "@sttracker/db/ids";
+import { toJson } from "@sttracker/db/json";
+
+/** Insert a user and return its id. */
+export async function makeUser(db: Db, username = "ada", preferences: Record<string, unknown> = {}): Promise<string> {
+  const id = newId();
+  const now = nowIso();
+  await db.k
+    .insertInto("users")
+    .values({
+      id,
+      username,
+      display_name: username,
+      password_hash: "x",
+      role: "member",
+      preferences: toJson(preferences),
+      created_at: now,
+      updated_at: now,
+    })
+    .execute();
+  return id;
+}
+
+/** Insert a work (shared unless `ownerUserId` is set) and return its id. */
+export async function makeWork(
+  db: Db,
+  opts: {
+    title?: string;
+    mediaType?: string;
+    year?: number | null;
+    parentId?: string | null;
+    ownerUserId?: string | null;
+    externalIds?: Record<string, string>;
+  } = {},
+): Promise<string> {
+  const id = newId();
+  const now = nowIso();
+  await db.k
+    .insertInto("works")
+    .values({
+      id,
+      media_type: opts.mediaType ?? "book",
+      title: opts.title ?? "Dune",
+      original_title: "",
+      year: opts.year ?? null,
+      release_date: null,
+      creators: toJson([]),
+      description: "",
+      cover_url: "",
+      cover_attachment_id: null,
+      metadata: toJson({}),
+      parent_id: opts.parentId ?? null,
+      position: null,
+      owner_user_id: opts.ownerUserId ?? null,
+      merged_into_id: null,
+      created_at: now,
+      updated_at: now,
+    })
+    .execute();
+  for (const [namespace, value] of Object.entries(opts.externalIds ?? {})) {
+    await db.k.insertInto("external_ids").values({ id: newId(), work_id: id, namespace, value }).execute();
+  }
+  return id;
+}