Make taste global by default to support Git worktrees

Feature Description

Currently taste is stored per worktree, so it’s not shared when using git worktree. Please make taste global by default

Use Case

I work with multiple worktrees across branches and need the same taste everywhere. Global taste avoids separate setups and missing data in each worktree, making the workflow smooth.

Additional Context

No response

How important is this to you?

Nice to have

首先，追蹤 taste 目前按每個 worktree 儲存的位置，以及該命令如何識別 Git worktree。在變更預設範圍之前，檢查現有的持久化與設定行為。完成的標準是：taste 預設在 repository 的各個 worktree 之間共用，而且目前的使用情境不需要額外設定即可運作。