Cody: Bot response multiplexer publishes, then completes turns

[dominiccooney]

The LLM interaction pushes text to the bot response multiplexer without waiting for the publishing to complete. If the turn ends before publishing is complete, the half-parsed buffer is echoed as-is. The net effect is that </selection> closing tags from fixups are sometimes echoed to the output.

This fixes the problem by chaining a promise for the publications together and waits for them to complete before doing the "turn complete" processing.

Test plan

cd client/cody-shared && pnpm test

Manual test:

This is racy, but you should use Fixup from Inline Instructions, Fixup (Experimental), etc. and check that the word </selection> does not appear in the output.

[abeatrix]

lgtm. everything works as expected with the new change and the stop generating button still works with chat and inline chat.

edit: also confirmed that the fixup output does not contain in the output