make folder to house worktrees configurable

Problem

At the moment, repositories and their worktrees need to exist under the same parent folder. This creates a workflow issue for users who use IDEs and other development tools.

For example, I keep my repositories in a directory that I open in IntelliJ IDEA and several other tools. When worktrees are created alongside the repositories, those tools detect each worktree as a separate Git project, cluttering the workspace with additional projects and diffs that I don't want to see.

Proposed Solution

It would be very helpful if the location where worktrees are created could be made configurable.

This would allow users to:

Keep their primary repository directory clean.
Store worktrees in a separate location dedicated to temporary or parallel work.
Avoid IDEs and other tooling automatically detecting every worktree as an additional Git project.

---
| Field | Value |
| --- | --- |
| App version | 1.0.22 |
| OS | macOS 26.4.1 |
| Theme | GitHub |
| Path | /chat |
| Tenure | Week 2 |

Beginne damit, den Ablauf zur Erstellung von Worktrees und die Konfigurationsoberfläche der App zu finden. Verfolge, wie der aktuelle übergeordnete Ordner ausgewählt wird, definiere dann ein konfigurierbares Ziel für neue Worktrees und stelle sicher, dass Repositories getrennt von ihren Worktrees bleiben können.

Vom Indexierungsmodell aus dem Issue-Text verfasst.