cmd/git(fix[Git.run]): Fix boolean config serialization typo

why: The stringify helper used `if True` instead of `if v`, causing all
boolean config values to serialize as "true" regardless of actual value.
what:
- Change `return "true" if True else "false"` to `if v else "false"`

Author: tony

src/libvcs/cmd/git.py

@@ -243,7 +243,7 @@ def run(
 
             def stringify(v: t.Any) -> str:
                 if isinstance(v, bool):
-                    return "true" if True else "false"
+                    return "true" if v else "false"
                 if not isinstance(v, str):
                     return str(v)
                 return v