Integrate the new address resolver into gt mail send:
- Resolves addresses to determine delivery mode (agent, queue, channel)
- Queue/channel: single message delivery
- Agent/group/pattern: fan-out to all resolved recipients
- Falls back to legacy routing if resolver fails
- Shows resolved recipients when fan-out occurs
Supports all new address types:
- Direct: gastown/crew/max
- Patterns: */witness, gastown/*
- Groups: @ops-team (beads-native groups)
- Queues: queue:work-requests
- Channels: channel:alerts
Part of gt-xfqh1e.10 (mail send update task).
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>