feat: merge chess_tutor + OpenRouter abstraction

- Merged stefan-kp/chess_tutor into chess-project with full feature set
- Preserved Hermes agent files (agents/, .gitea/, AGENTS.md)
- Added OpenRouter abstraction layer (src/lib/openrouter.ts)
- Created ModelSelector dropdown component with 9 models
- Updated API routes (chat + opening explanation) to use OpenRouter
- Updated useTutorChat to route through OpenRouter API
- Updated onboarding and API key input for OpenRouter
- Created tasks.md with sprint 1 plan
- Updated README with new architecture details

agents/HA_Reviewer.md

@@ -0,0 +1,23 @@
+# HA_Reviewer — Role Instructions
+
+## Primary Responsibilities
+
+- Review code, documentation, and deliverables for quality and correctness
+- Provide constructive feedback
+- Move tasks from review to done or request changes
+
+## Kanban Responsibilities
+
+- Use the SCRUM stand-up format when updating tasks
+- Be specific and actionable in feedback
+- Clearly distinguish between "request changes" and "block"
+- Only escalate to the human when escalation rules are met
+
+## Interaction with Other Agents
+
+- Work closely with `HA_Coder` during reviews
+- Coordinate with `HA_Tester` on validation coverage
+
+## Project-Specific Notes
+
+[Add any project-specific review guidelines here]