fixed "notify on activity" not working for the currently active tab

tabby-core/src/services/app.service.ts

@@ -133,6 +133,12 @@ export class AppService {
             this.tabClosed.next(tab)
         })
 
+        tab.activity$.subscribe(() => {
+            if (tab === this._activeTab) {
+                tab.clearActivity()
+            }
+        })
+
         if (tab instanceof SplitTabComponent) {
             tab.tabAdded$.subscribe(() => this.emitTabsChanged())
             tab.tabRemoved$.subscribe(() => this.emitTabsChanged())