[Feature Request] Configurable worktree directory location with sibling directory support

Bug Description
Please provide a way to configure where worktrees go, specifically a sibling directory. I asked Claude what is the recommended location for worktrees, and it said: "The widely recommended convention is to put worktrees in a sibling directory to the main repository, not inside it." Using a subdirectory like you do now causes problems.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.50
• Feedback ID: f0086445-61db-4342-b4ea-df9fff886599

Errors

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