fix: use strict int type check to satisfy static type checker

Pyright correctly flags that `isinstance(to, bool)` doesn't narrow the
`str | int` union since `bool` is a subclass of `int`. Use `type(to) is int`
for a strict exact-type check that both satisfies the type checker and
correctly excludes booleans.

Author: Archmonger

src/reactpy_router/components.py

@@ -110,7 +110,7 @@ def _navigate(to: str | int, replace: bool = False) -> VdomDict | None:
     def on_navigate_callback(_event: dict[str, Any]) -> None:
         set_location(Location(**_event))
 
-    if isinstance(to, int) and not isinstance(to, bool):
+    if type(to) is int:
         # Integer navigation (go back/forward) — always delegate to JS;
         # the resulting popstate event is handled by the History component.
         return Navigate({"onNavigateCallback": on_navigate_callback, "to": to, "replace": replace})