HooksMixin(fix[show_hook]): Strip % prefix for control-mode hooks

why: Control-mode hooks like %output, %window-add have % prefix that
Hooks.from_stdout() strips when creating attributes, but show_hook()
didn't strip it before lookup, causing all %-prefixed hooks to return
None.

what:
- Add lstrip("%") before replace("-", "_") in show_hook() attribute lookup

Author: tony

src/libtmux/hooks.py

@@ -432,7 +432,7 @@ def show_hook(
         if hooks_output is None:
             return None
         hooks = Hooks.from_stdout(hooks_output)
-        return getattr(hooks, hook.replace("-", "_"), None)
+        return getattr(hooks, hook.lstrip("%").replace("-", "_"), None)
 
     def set_hooks(
         self,