Git Worktree Setup

Start implementation in an isolated workspace without taking ownership of a worktree that the user or harness already manages.

Quick Path

1. Read repository instructions and inspect Git state before changing anything.
2. Detect whether the current checkout is already a linked worktree, including the submodule exception below. Reuse it when it is.
3. If isolation is not already present, create it only when the user has asked for a worktree or consents to one.
4. Prefer the harness's native worktree capability. Fall back to git worktree only when no native capability exists.
5. Run repository-defined setup and the smallest meaningful baseline check.
6. Report the path, branch state, creation mechanism, and validation evidence.

Detect Existing Isolation