v1.40.0 - Auto-close worktree by default

Breaking Changes

• Default behavior changed: Worktree is now automatically cleaned up after the Claude session ends
• The -c/--auto-close flag has been replaced with -k/--keep

How to migrate

If you were using cis 123 and expecting the worktree to stay open, now use:

cis 123 -k
# or
cis 123 --keep

Why this change?

Most users want the worktree cleaned up after the PR is created. Keeping the worktree open is now the exception rather than the default.