fix(practice): include endEarly.data in currentPlan priority chain

The stop button wasn't working because endEarly.data was not included
in the currentPlan derivation chain. When the mutation completed with
the updated plan (completedAt set), the view didn't update to 'summary'.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/app/practice/[studentId]/StudentPracticeClient.tsx

@@ -135,6 +135,7 @@ export function StudentPracticeClient({
   // Current plan from mutations or fetched data (priority order)
   // Mutations take priority (most recent user action), then fetched/cached data
   const currentPlan =
+    endEarly.data ??
     recordResult.data ??
     startPlan.data ??
     approvePlan.data ??