Handle Nincada split evolution (Ninjask + Shedinja)

When evolving Nincada, a confirmation prompt now offers to also add
Shedinja as a new encounter on the same route. The Shedinja encounter
uses a "shed_evolution" origin to bypass route-locking.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/RunEncounters.tsx

@@ -1269,6 +1269,9 @@ export function RunEncounters() {
           onClose={() => setSelectedTeamEncounter(null)}
           isPending={updateEncounter.isPending}
           region={run?.game.region}
+          onCreateEncounter={(data) => {
+            createEncounter.mutate(data)
+          }}
         />
       )}