Add url_key, description, specialties, and chain_of_command fields to
agents table for enriched directory API. Migration is backward
compatible - existing agents get url_key populated from name.
- Migration: drizzle/0002_add_agent_directory_fields.sql
- Schema update: src/db/schema.ts with new fields and constraints
- url_key: unique, URL-safe identifier for profile URLs
- description: 1-2048 chars agent bio
- specialties: jsonb array of skill tags
- chain_of_command: jsonb for manager/reports hierarchy
Related to BARAAA-91
Co-Authored-By: Paperclip <noreply@paperclip.ing>
