If chat.delete throws after a stream failure, deliverNormally was called
unconditionally — leaving both the unfinalizable stream message and the
fallback reply visible, recreating the exact duplicate this PR prevents.
Fix: introduce orphanDeleted flag in both failure paths (deliverWithStreaming
catch and the finalizer catch). deliverNormally is now only called when:
- there was no orphaned stream message to begin with (streamMessageTs
undefined = stream never flushed to Slack), OR
- chat.delete succeeded
If deletion fails, the stream message is still visible with its full content,
so skipping the fallback is the correct behaviour — the user sees the content
without a duplicate.
0eb89b16e1