fix(discord): recover existing thread on 160004 error

[saschabuehrle]

Bug

#279 — createDiscordThread silently fails when Discord returns error code 160004 ("A thread has already been created for this message"), leaving discordThreadId as undefined. The bot then posts a standalone channel message instead of replying in the existing thread.

Fix

Added error recovery inside createDiscordThread for the specific 160004 error code. When Discord reports that a thread already exists for a message, the method now returns the existing thread's ID (which equals the parent message ID in Discord's threading model) instead of letting the error propagate.

This handles all call sites at once — both the webhook handler and the gateway handler benefit from the recovery without needing individual catch-block changes.

Other Discord API errors continue to propagate normally.

Testing

Verified that:

• NetworkError with "160004" in the message triggers the recovery path
• The returned thread ID matches the parent message ID (Discord's documented behavior)
• Non-160004 errors still propagate to callers unchanged

Happy to address any feedback.

Greetings, saschabuehrle

[vercel]

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