fix(init): guard learnTimer callback against post-teardown execution

Prevent a race where a queued learnTimer callback fires after
tearDown() has completed, creating an orphaned tipTimer interval.

Author: getsentry-bot

src/lib/init/ui/ink-ui.ts

@@ -816,6 +816,9 @@ export class InkUI implements WizardUI {
   private startLearnSequence(): void {
     const store = this.store;
     this.learnTimer = setInterval(() => {
+      if (this.torndown) {
+        return;
+      }
       const { learnState } = store.getSnapshot();
       if (learnState.complete) {
         this.stopLearnSequence();