feat(worktree): add interactive delete command

[nettee]

Summary

• add interactive wtk delete with TTY-only multi-select and exact Y confirmation
• support standalone and coordinated worktree deletion while preserving branches
• add PTY-backed e2e coverage and update Zest spec/docs

Verification

• cargo fmt --check
• cargo check
• cargo test
• uv run pytest e2e/test_interactive_delete.py e2e/test_repo_mode.py e2e/test_auxiliary_group.py