Patch release that adds --ref / --worktree-ref to let users base a new worktree on a specific branch, tag, or commit.
Changelog
[new] Added --ref and --worktree-ref flags. When used with --worktree, these specify the branch, tag, or commit the new worktree should be based on (defaults to the current HEAD of the source checkout when omitted).
[changed] Updated shell completions (bash, zsh, fish, elvish, PowerShell) to recognize the new flags.
[changed] Updated user guide sections on getting started and headless mode to document the new flags and show example usage.
Under the hood
Bumped internal version metadata and bundled manifest checksums to 0.2.65.
