Add architecture critique and channel integration guide

- ARCHITECTURE_CRITIQUE.md: Honest assessment of OB1 complexity, three
  MCP alternatives with ASCII diagrams, decision matrix, recommendations
  by user type
- CONNECTING_CHANNELS.md: Complete integration guide for 8+ channels
  (Slack, Telegram, Discord, Email, Obsidian, WhatsApp, SMS) with
  full copy-paste Edge Function code, generic template for adding
  any channel in 15 minutes

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

Author: az9713