refactor(features): split entities into models/ + errors/ subdirs

All 5 features (auth, blog, marketing-pages, navigation; media has no
entities yet) now follow Lazar's pattern:
- entities/<x>.ts → entities/models/<x>.ts
- entities/errors.ts → entities/errors/<domain>.ts + errors/common.ts

Updates all import paths across factories, contracts, tests, use cases,
controllers, repositories, integrations, and src/index.ts exports.

navigation divergence: had no errors.ts; errors/header.ts +
errors/common.ts added as new forward-looking stubs.

Refactor log: docs/superpowers/refactor-logs/2026-05-05-lazar-pattern-conformance.md
Spec: §5, §9.3

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/marketing-pages/src/entities/models/page.test.ts

@@ -0,0 +1,58 @@
+import { describe, expect, it } from "vitest";
+import { pageSchema, pageStatusSchema } from "./page";
+
+describe("pageSchema", () => {
+  it("accepts a minimal valid page", () => {
+    const result = pageSchema.parse({
+      id: "p1",
+      title: "About",
+      slug: "about",
+      hero: { heading: "About us" },
+      layout: [],
+      seo: { title: "About — My App" },
+      createdAt: new Date(),
+      updatedAt: new Date(),
+    });
+    expect(result.status).toBe("draft");
+    expect(result.publishedAt).toBeNull();
+  });
+
+  it("accepts a published page with publishedAt", () => {
+    const result = pageSchema.parse({
+      id: "p1",
+      title: "About",
+      slug: "about",
+      hero: { heading: "About us" },
+      layout: [],
+      status: "published",
+      publishedAt: new Date(),
+      seo: { title: "About" },
+      createdAt: new Date(),
+      updatedAt: new Date(),
+    });
+    expect(result.status).toBe("published");
+    expect(result.publishedAt).toBeInstanceOf(Date);
+  });
+
+  it("rejects empty title", () => {
+    expect(() =>
+      pageSchema.parse({
+        id: "p1",
+        title: "",
+        slug: "about",
+        hero: { heading: "h" },
+        layout: [],
+        seo: { title: "x" },
+        createdAt: new Date(),
+        updatedAt: new Date(),
+      }),
+    ).toThrow();
+  });
+});
+
+describe("pageStatusSchema", () => {
+  it("accepts draft and published", () => {
+    expect(pageStatusSchema.parse("draft")).toBe("draft");
+    expect(pageStatusSchema.parse("published")).toBe("published");
+  });
+});