Trim AGENTS.md to focus on actionable content

Remove bloated sections (full module map, feature inventory, deployment
details, health checks) that waste context window. Keep only what an AI
agent needs: build/test commands, policy interface, coding conventions,
and key gotchas.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: Tharsanan1