Design System: Document patterns for sidebars

## Description
We are migrating our design system to Storybook, with a primary focus on documenting common patterns to help answer the question: “How should something be implemented?”.

The focus of this issue is the pattern for sidebars.

1. Inventory existing implementations
- [ ] Identify current implementations and variations
- [ ] Group them by the problems they solve

2. Define target patterns
- [ ] Define the ideal solution for each problem. Ensure solutions stay close to existing implementations, allowing small improvements (e.g., button placement)

3. Document in Storybook
- [ ] Document each solution. Clearly describe when to use each one

4. Handle discrepancies
- [ ] Address minor gaps directly during implementation
- [ ] Create follow-up issues for larger discrepancies (e.g., preferred solution not consistently used)