Replace 4 stub gRPC handlers with real implementations: - GetAllocation: re-computes allocation from latest asset selection via PortfolioAllocator - RebalancePortfolio: compares target vs current positions, generates drift-based actions - GetAgentPerformance: queries agent_orders for P&L, win rate, Sharpe, max drawdown - StreamAgentActivity: sends 5-second heartbeat events until client disconnects Trading agent service: 14/15 endpoints now have real implementations. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>