Orphaned-reply handling is Teams-only

InboundHandler.handleReply has a fallback: when a reply arrives and no ticket matches its thread, it creates a ticket and persists the message — but never answers it. The reasoning is that dropping a customer's words is worse than filing an oddly-titled ticket a human can pick up.

That reasoning is written as a general principle. In practice only one platform reaches it.

So a customer message that arrives without a matching ticket is preserved on Teams and email, and silently discarded on Discord, Slack and GitHub.

Why it matters

The discard cases are not hypothetical. Any thread that predates Outpost's deployment in a channel has no ticket, so every reply in it is dropped. Same for a thread whose ticket was deleted, and for a reply that arrives before its own thread-create event.

Nobody notices, because dropping is silent by construction — there is no error, no ticket, and no log the team watches.

The decision

Three defensible answers, and it is a product call:

1. Unify on preserve. Remove the pre-filters so every platform files the ticket. Costs: some noise from threads Outpost was never meant to see, and each ticket is titled with a mid-conversation fragment.
2. Unify on drop. Remove the fallback and accept that an untracked reply is not ours. Simpler, and arguably correct if channels are deliberately scoped — but it loses real customer messages.
3. Keep the split deliberately, on the grounds that Teams and email are lower-volume and higher-value than a public Discord. That is a legitimate position; it just needs to be stated rather than inherited from whoever wrote each pre-filter first.

The current comment in platforms/inbound.ts documents which platforms reach the branch, so the code is at least honest. This issue is about picking one.

Related: #174 (human-presence gate) touches the same code path and may change what "should we answer this" means.

Start with platforms/inbound.ts and trace InboundHandler.handleReply alongside events/message-create.ts, events/message.ts, webhooks/issue-comment.ts, and postmark/route.ts. First resolve which untracked-reply behavior is intended, considering related issue #174; done means the chosen policy is implemented consistently and covered for each listed platform.