GeezerVison

• Shortcut other steps if one holds the output - We had a bug in the output pipeline where if one step returned [] meaning that the output chunk should be held off, all the current chunks would continue to run and potentially modify the context.
• Shortcut buffered PII sooner, as soon as the buffer can't be a UUID - Our PII refaction format is #UUID#. Our code was finding an opening #, then checking for a closing matching # or end of the output. For copilot, however, this meant that we were buffering the whole file, because the filename comes in this format:

# filepath: /Users/jakub/devel/demo-repo-python/app.py

This means we would keep searching for the closing hash which never
came. Instead, buffer only as long as the context between the hashes can
reasonably be a UUID.

Fixes: #1250