Adapter: Implement Postgres adapter

Overview

Create Postgres adapter for production-grade, scalable storage.

Characteristics

• Production-grade relational DB
• Best for large teams, high volume
• Advanced querying, scalability
• Connect to existing Postgres infrastructure

Implementation

• Create src/adapters/postgres.ts
• Implement EvaliteAdapter interface using postgres client (e.g., pg or postgres)
• Create schema migration for tables (runs, evals, results, scores, traces)
• Support connection config (url, pool settings, etc.)
• Export createPostgresAdapter(opts) helper
• Add tests using multi-adapter test suite
• Document usage examples

Configuration

interface PostgresAdapterOpts {
  connectionString?: string;
  host?: string;
  port?: number;
  database?: string;
  user?: string;
  password?: string;
  ssl?: boolean;
  maxConnections?: number;
}

Related

Part of adapter API refinement (#218)

Start by reading adapter API refinement issue #218 and the EvaliteAdapter interface, then inspect the planned entry point at src/adapters/postgres.ts. Implement the connection options, schema migration, factory export, tests using the multi-adapter test suite, and usage documentation; done means all listed Postgres adapter capabilities are covered.