Clone operations now use a temp directory to completely isolate from
any git repository at the process cwd. This fixes the issue where
`.git` directory was deleted during `gt rig add` when the town root
was initialized with `--git`.
The fix applies to all four clone functions:
- Clone()
- CloneBare()
- CloneWithReference()
- CloneBareWithReference()
Each function now:
1. Creates a temp directory
2. Runs clone inside temp dir with cmd.Dir set
3. Sets GIT_CEILING_DIRECTORIES to prevent parent repo discovery
4. Moves the cloned repo to the final destination
eb8024c1f9