Add 'Select directory' button to Diffs view

Author: dpen2000 Channel: #shelley Link: https://discord.com/channels/1405685085923049482/1450334528210993295/1497456102751604939

Request

Add a "Select directory" button to the Diffs view, similar to what exists elsewhere in the UI.

Context

The user notes this would be useful for:

• Convenience: Ability to quickly change directories without leaving the current view
• Consistency: This UI pattern exists in other parts of the application
• Practical use case: When working in a subdirectory of a git repository and encountering "not a git repository" errors, being able to select the correct directory from the Diffs view would be more efficient than having to cd manually

The implementation should be mindful of keeping the Diffs graph intentionally light on UI chrome, so placement and design should be carefully considered.