OptionsMixin(fix[show_option]): Forward legacy g parameter

why: The g parameter was accepted but silently ignored, breaking
backward compatibility for callers using the legacy API
what:
- Forward g parameter to _show_option() via global_ or g
- Ensures show_option("foo", g=True) works as expected

Author: tony

src/libtmux/options.py

@@ -1210,7 +1210,7 @@ def show_option(
         """
         return self._show_option(
             option=option,
-            global_=global_,
+            global_=global_ or g,
             scope=scope,
             ignore_errors=ignore_errors,
             include_hooks=include_hooks,