Fix high CPU usage from notifications and add regression tests

- Fix auto-updating Text(date, style: .time) causing continuous SwiftUI updates
  by using static formatting with .formatted(date:time:)
- Fix notification popover keeping SwiftUI observers active when closed by
  clearing contentViewController on popover close and recreating on open
- Fix focus loss when notifications arrive while typing by only setting
  focus in NotificationsPage when the page is visible
- Make Update Pill and Update Logs debug-only features
- Add CPU regression tests: test_cpu_usage.py, test_cpu_notifications.py
- Add lint test for auto-updating Text patterns: test_lint_swiftui_patterns.py

Sources/WindowToolbarController.swift

@@ -123,6 +123,7 @@ final class WindowToolbarController: NSObject, NSToolbarDelegate {
             return item
         }
 
+        #if DEBUG
         if itemIdentifier == updateItemIdentifier, let updateViewModel {
             let item = NSToolbarItem(itemIdentifier: itemIdentifier)
             let view = NonDraggableHostingView(rootView: UpdatePill(model: updateViewModel))
@@ -138,6 +139,7 @@ final class WindowToolbarController: NSObject, NSToolbarDelegate {
                 }
             return item
         }
+        #endif
 
         return nil
     }