Please add an option to NEVER create worktree

Please add an option to NEVER create worktree

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| Field | Value |
| --- | --- |
| App version | 1.1.3 |
| OS | macOS 26.5.2 |
| Theme | GitHub |
| Path | / |
| Tenure | Week 9 |

The issue names no files, tests, or entry points. First locate where worktrees are created and where app options are defined, then clarify the expected scope of the setting. Done should be verified by tests showing that enabling the option prevents worktree creation.

索引モデルが issue の本文から書いたものです。