Notification triage

Declares Agent/NotificationTriage standing: decides per recipient whether a notification escalates to email or Teams.

• Agent path: Agent/NotificationTriage
• Purpose: Decides, per the recipient's own rules, whether a new notification also goes to email or Teams, and creates the delivery nodes; runs on a small model.
• Triggers: Every new in-app notification whose recipient's rules may call for escalation (NotificationTriageService)
• Runs on: every portal with notification channels
• Wired: yes
• Thread namespace: {recipient}/_Triage
• Note: One headless thread per escalated notification, in the RECIPIENT's own `_Triage` namespace — there is no shared queue or ledger to read.