workshop: add Chapter 4 preview stubs (artifact server handlers)

- Add artifacts/flashcard/server.ts with schema and TODO for handler
- Add artifacts/study-plan/server.ts with schema and TODO for handler
- Type definitions ready for Chapter 4 implementation

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: NiallJoeMaher

artifacts/flashcard/server.ts

@@ -0,0 +1,34 @@
+// TODO CHAPTER 4: Implement flashcard server handler
+//
+// This file should:
+// 1. Define FlashcardData type schema
+// 2. Create document handler for flashcard artifacts
+// 3. Handle creation and updates of flashcard quizzes
+//
+// See CHAPTER-4.md for the complete implementation.
+
+import { z } from "zod";
+
+/**
+ * Schema for flashcard quiz data
+ */
+export const flashcardSchema = z.object({
+  topic: z.string(),
+  questions: z.array(
+    z.object({
+      question: z.string(),
+      options: z.array(z.string()).length(4),
+      correctAnswer: z.number().min(0).max(3),
+      explanation: z.string(),
+    })
+  ),
+});
+
+export type FlashcardData = z.infer<typeof flashcardSchema>;
+
+// TODO: Add createDocumentHandler for flashcard artifacts
+// export const flashcardDocumentHandler = createDocumentHandler<"flashcard">({
+//   kind: "flashcard",
+//   onCreateDocument: async ({ title, dataStream }) => { ... },
+//   onUpdateDocument: async ({ document, description, dataStream }) => { ... },
+// });

artifacts/study-plan/server.ts

@@ -0,0 +1,44 @@
+// TODO CHAPTER 4: Implement study-plan server handler
+//
+// This file should:
+// 1. Define StudyPlanData type schema
+// 2. Create document handler for study-plan artifacts
+// 3. Handle creation and updates with progress tracking
+//
+// See CHAPTER-4.md for the complete implementation.
+
+import { z } from "zod";
+
+/**
+ * Schema for study plan data
+ */
+export const studyPlanSchema = z.object({
+  topic: z.string(),
+  duration: z.string(),
+  overview: z.string(),
+  weeks: z.array(
+    z.object({
+      week: z.number(),
+      title: z.string(),
+      goals: z.array(z.string()),
+      tasks: z.array(
+        z.object({
+          task: z.string(),
+          duration: z.string(),
+          completed: z.boolean().default(false),
+        })
+      ),
+      resources: z.array(z.string()),
+    })
+  ),
+  tips: z.array(z.string()),
+});
+
+export type StudyPlanData = z.infer<typeof studyPlanSchema>;
+
+// TODO: Add createDocumentHandler for study-plan artifacts
+// export const studyPlanDocumentHandler = createDocumentHandler<"study-plan">({
+//   kind: "study-plan",
+//   onCreateDocument: async ({ title, dataStream }) => { ... },
+//   onUpdateDocument: async ({ document, description, dataStream }) => { ... },
+// });