docs: clarify Interactive Demo uses mock data, not real OpenRouter

Update documentation to reflect demo simulation status:

README.md: Add note explaining demo uses static mock data
CHANGELOG.md: Add Interactive Demo entry marked as Mock
roadmap_ideas.md: Update status to in-evaluation with priority note

Prevents user confusion about AI capabilities in demo section.

Refs: Sprint 3, demo clarification

CHANGELOG.md

@@ -17,6 +17,15 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   - Add Tailwind directives to src/index.css
   - Ready for component development and styling
 
+- feat: Add Interactive Demo section to Landing Page (Mock)
+  - Two-column layout: Terminal input + AI analysis output
+  - 3 preset log examples (PostgreSQL OOM, Nginx 502, Node.js Exception)
+  - Simulated 1.5s AI analysis delay with loading animation
+  - Copy-to-clipboard functionality for suggested commands
+  - Fully accessible with aria-live and screen reader support
+  - Note: Uses static mock data, NOT real OpenRouter API calls
+  - Real AI integration planned for future (see docs/roadmap_ideas.md)
+
 - feat: Create n8n workflow `LogWhisperer_Ingest` for secure log ingestion
   - Webhook trigger on POST `/webhook/logwhisperer/ingest`
   - HMAC-SHA256 signature validation with anti-replay protection