Refactor email routing to a strategy-chain pattern with fallback conversation creation

Refactor email routing to a strategy-chain pattern with fallback conversation creation: a task in bird-critic-1.5-full-300 (Harbor dataset). Chatwoot is a Rails customer support platform at /workspace/repo that receives inbound emails via Action Mailbox. The existing ApplicationMailbox routes…

The task

Chatwoot is a Rails customer support platform at `/workspace/repo` that receives inbound emails via Action Mailbox. The existing `ApplicationMailbox` routes emails either to `ReplyMailbox` (pattern-matched reply addresses) or `SupportMailbox` (channel-addressed emails). This split forces routing decisions to be made…

Part of kochsnow/bird-critic-1.5-full-300.