Initial commit: Brachnha Insight project setup

- Next.js 14+ with App Router and TypeScript
- Tailwind CSS and ShadCN UI styling
- Zustand state management
- Dexie.js for IndexedDB (local-first data)
- Auth.js v5 for authentication
- BMAD framework integration

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

tests/unit/prompt-engine.test.ts

@@ -0,0 +1,28 @@
+import { describe, it, expect } from 'vitest';
+// @ts-ignore - Module likely not created yet
+import { PromptEngine } from '@/lib/llm/prompt-engine';
+
+describe('PromptEngine (Ghostwriter)', () => {
+    it('should construct a grounded prompt with user insight', () => {
+        // GIVEN: A user insight and chat history
+        const history = [
+            { role: 'user', content: 'I feel stupid.' },
+            { role: 'assistant', content: 'Why?' },
+            { role: 'user', content: 'I made a typo.' }
+        ];
+        const insight = "I need a checklist for typos.";
+
+        // WHEN: Constructing the prompt
+        // @ts-ignore
+        const prompt = PromptEngine.constructGhostwriterPrompt(history, insight);
+
+        // THEN: The system prompt should enforce grounding
+        expect(prompt[0].role).toBe('system');
+        expect(prompt[0].content).toContain('You are an expert Ghostwriter');
+        expect(prompt[0].content).toContain('Ground your answer in the user insight'); // R-2.1 Mitigation
+
+        // AND: The user insight should be clearly labeled
+        const lastMessage = prompt[prompt.length - 1];
+        expect(lastMessage.content).toContain(`INSIGHT: ${insight}`);
+    });
+});