feat: add model tracking and reporting across pipeline

- Track actual model name from router through audit logs, session.json, and query output
- Add router-utils.ts to resolve model names from ROUTER_DEFAULT env var
- Inject model info into final report's Executive Summary section
- Update documentation with supported providers, pricing, and config examples
- Update router-config.json with latest model versions (GPT-5.2, Gemini 2.5, etc.)

src/temporal/shared.ts

@@ -17,6 +17,7 @@ export interface AgentMetrics {
   outputTokens: number | null;
   costUsd: number | null;
   numTurns: number | null;
+  model?: string | undefined;
 }
 
 export interface PipelineSummary {