cmd/git(fix[Git.run]): Iterate -C paths instead of appending list

why: The -C flag was appending a list object as the second element,
creating invalid argv like ["git", "-C", ["path1", "path2"]] which
subprocess cannot handle. Git requires separate -C flags for each path.
what:
- Iterate over normalized C list and append -C for each path

Author: tony

src/libvcs/cmd/git.py

@@ -236,8 +236,8 @@ def run(
         if C is not None:
             if not isinstance(C, list):
                 C = [C]
-            C = [str(c) for c in C]
-            cli_args.extend(["-C", C])
+            for c in C:
+                cli_args.extend(["-C", str(c)])
         if config is not None:
             assert isinstance(config, dict)