feat: add AI test assistant dashboard

[PavelShilin89]

Summary

• Web dashboard (localhost:3000) with chat UI powered by Claude API
• AI can generate tests, run them, fix failures, and create PRs
• 7 tools: list_tests, read_file, write_file, run_tests, git_status, create_branch, create_pr
• Dark/light theme, SSE streaming, sidebar with test list and git status
• Minimal deps: express, @anthropic-ai/sdk, dotenv, tsx

Usage

cp .env.example .env  # add ANTHROPIC_API_KEY
npm install
npm run assistant      # open http://localhost:3000