bug: slinging work to a non-git rig automatically does `git init` but not to a non-git city

[csells]

Before you continue

• I searched existing issues and did not find a duplicate.
• I read the relevant docs and contributor guidance.

Gas City version

main@1fa5ec18

Environment

mac0s

Reproduction

~/my-project
$ gc sling claude "Add a README.md with a project description"
Created mp-ff9 — "Add a README.md with a project description"
Attached wisp mp-6yh (default formula "mol-do-work") to mp-ff9
Auto-convoy mp-4tl
Slung mp-ff9 → my-project/claude

~/my-project
$ ls
README.md

~/my-project (main)
$

Expected behavior

NOT to automatically turn a rig into a git repo, just like it doesn't turn a city into a git repo.

Actual behavior

automatically turns a rig folder into a git repo but does NOT do the same for a city folder.

Logs, screenshots, or traces

Additional context

the cause is likely that rigs aren't initialized with .beads folders and cities are. seems like creating the .beads for a rig would unify the behavior.