fix: followup: add once option to subscription tier watcher in PostHogTelemetryProvider (#9835)

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

src/platform/telemetry/providers/cloud/PostHogTelemetryProvider.ts

@@ -222,7 +222,7 @@ export class PostHogTelemetryProvider implements TelemetryProvider {
           this.posthog.people.set({ subscription_tier: tier })
         }
       },
-      { immediate: true }
+      { immediate: true, once: true }
     )
   }