feat(10-02): mount KB and calendar routers, update tool registry and prompt builder

- Mount kb_router and calendar_auth_router on gateway (Phase 10 agent capabilities)
- Update calendar_lookup tool schema with action/event_summary/event_start/event_end params
- Add tool result formatting instruction to build_system_prompt when tools assigned (CAP-06)
- Add kb_router and calendar_auth_router to shared/api/__init__.py exports
- Confirm CAP-04 (http_request) and CAP-07 (audit logging) already working

packages/gateway/gateway/main.py

@@ -17,6 +17,8 @@ Endpoints:
   GET  /api/portal/tenants/{id}/llm-keys  — BYO LLM key management
   GET  /api/portal/usage/*                — Usage and cost analytics
   POST /api/webhooks/*                    — Stripe webhook receiver
+  GET  /api/portal/kb/*                   — Knowledge base document management
+  GET  /api/portal/calendar/*             — Google Calendar OAuth endpoints
   GET  /health                            — Health check
 
 Startup sequence:
@@ -43,9 +45,11 @@ from gateway.channels.web import web_chat_router
 from gateway.channels.whatsapp import whatsapp_router
 from shared.api import (
     billing_router,
+    calendar_auth_router,
     channels_router,
     chat_router,
     invitations_router,
+    kb_router,
     llm_keys_router,
     portal_router,
     push_router,
@@ -164,6 +168,12 @@ app.include_router(web_chat_router)   # WebSocket: /chat/ws/{conversation_id}
 # ---------------------------------------------------------------------------
 app.include_router(push_router)       # Push subscribe/unsubscribe/send
 
+# ---------------------------------------------------------------------------
+# Phase 10 Agent Capabilities routers
+# ---------------------------------------------------------------------------
+app.include_router(kb_router)             # KB documents: /api/portal/kb/{tenant_id}/documents
+app.include_router(calendar_auth_router)  # Google Calendar OAuth: /api/portal/calendar/*
+
 
 # ---------------------------------------------------------------------------
 # Routes