feat: complete phase 2 -- multi-agent routing, interrupt TTL, escalation, templates

- Intent classification with LLM structured output (single/multi/ambiguous)
- Discount agent with apply_discount and generate_coupon tools
- Interrupt manager with 30-min TTL auto-expiration and retry prompts
- Webhook escalation module with exponential backoff retry (max 3)
- Three vertical industry templates (e-commerce, SaaS, fintech)
- Template loading in AgentRegistry
- Enhanced supervisor prompt with dynamic agent descriptions
- 153 tests passing, 90.18% coverage

backend/app/agents/fallback.py

@@ -1,4 +1,4 @@
-"""Fallback agent tools -- handles unmatched intents."""
+"""Fallback agent tools -- handles unmatched intents and clarification requests."""
 
 from __future__ import annotations
 
@@ -13,6 +13,7 @@ def fallback_respond(query: str) -> str:
         "Here's what I can do:\n"
         "- Check order status (e.g., 'What is the status of order 1042?')\n"
         "- Get tracking information (e.g., 'Track order 1042')\n"
-        "- Cancel an order (e.g., 'Cancel order 1042')\n\n"
+        "- Cancel an order (e.g., 'Cancel order 1042')\n"
+        "- Apply discounts or generate coupons\n\n"
         "Could you please rephrase your request?"
     )