Implements agent scorecard system that tracks and summarizes agent performance:
- Track issues touched, PRs opened/merged, tests affected, tokens earned/spent
- Generate compact scorecards for daily or weekly periods
- Pattern detection: high/low merge rates, silent workers, token accumulation
- API endpoints for programmatic access (/scorecards/api/*)
- HTML dashboard with HTMX-powered live updates
- Added navigation link in both desktop and mobile menus
New modules:
- dashboard/services/scorecard_service.py: Core scoring logic
- dashboard/routes/scorecards.py: API and HTML routes
- templates/scorecards.html: Dashboard UI
- tests/dashboard/test_scorecards.py: Comprehensive test suite
Refs #712