Feature: Improve One-sided strategy funding UX

# Description
Users seem confused about how to create one-sided strategies.

Currently, the flow is to just select 0 brackets on one side. Users tried negative numbers, 0 funding and other tricks which didnt work.

# Requirements
TBD (Solution not clear)
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# Background
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No files, tests, or entry points are named. First inspect the existing strategy-creation flow and how one-sided funding is represented, then clarify the intended UX and acceptance criteria with maintainers. Done should mean users can create one-sided strategies through an explicit, verified flow without undocumented workarounds.

Written by the indexing model from the issue text.