Never cross worktree boundaries

All work in a session must stay within the current working directory's OreStudio checkout (e.g. local4). Never cd into or use git -C to operate on another checkout (local1, local2, local3, remote).

Why: Crossing into local2 during sprint 19 caused a commit to land on feature/delete-get-trade-detail (an unrelated in-flight branch) instead of feature/commission-currency, silently corrupting someone else's work in progress.

How to apply: If a branch is already checked out in another worktree (git refuses with "already used by worktree at …"), do NOT go to that worktree. Instead: (1) flag the conflict to the user, (2) offer to pick a different task or create a fresh branch from origin/main within the current checkout.