Compatibility with other mods that process chat

Due to the way Synapse deduplicates/formats chat messages, CivRelay, AdvancedMacros, Macromod, and other mods do not observe any snitch/group/... chat messages.

Possible solutions:

- Instead of writing formatted chat messages directly to the GUI, Synapse could send a fake packet to the NetHandler.
- Synapse could publish events that other mods can listen for.

Note that chat messages don't only originate from the Minecraft server, but also from other clients connected via the relay server. This means that merely formatting synchronously in the chat handler isn't enough.

Start by tracing how Synapse formats and sends chat messages to the GUI, including messages from the Minecraft server and clients connected through the relay server. Compare the fake NetHandler packet and published-event approaches, then verify that CivRelay, AdvancedMacros, Macromod, and similar mods can observe all snitch and group chat messages.

Written by the indexing model from the issue text.