Fix UI test failures: registration dismiss cascade, onboarding reset, test stability

- Fix registration flow dismiss cascade: chain fullScreenCover → sheet onDismiss
  so auth state is set only after all UIKit presentations are removed, preventing
  RootView from swapping LoginView→MainTabView behind a stale sheet
- Fix onboarding reset: set hasCompletedOnboarding directly instead of calling
  completeOnboarding() which has an auth guard that fails after DataManager.clear()
- Stabilize Suite1 registration tests, Suite6 task tests, Suite7 contractor tests
- Add clean-slate-per-suite via AuthenticatedUITestCase reset state
- Improve test account seeding and screen object reliability

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

iosApp/HoneyDueUITests/Suite6_ComprehensiveTaskTests.swift

@@ -22,9 +22,25 @@ final class Suite6_ComprehensiveTaskTests: AuthenticatedUITestCase {
 
     // Test data tracking
     var createdTaskTitles: [String] = []
+    private static var hasCleanedStaleData = false
 
     override func setUpWithError() throws {
         try super.setUpWithError()
+
+        // Dismiss any open form from previous test
+        let cancelButton = app.buttons[AccessibilityIdentifiers.Task.formCancelButton].firstMatch
+        if cancelButton.exists { cancelButton.tap() }
+
+        // One-time cleanup of stale tasks from previous test runs
+        if !Self.hasCleanedStaleData {
+            Self.hasCleanedStaleData = true
+            if let stale = TestAccountAPIClient.listTasks(token: session.token) {
+                for task in stale {
+                    _ = TestAccountAPIClient.deleteTask(token: session.token, id: task.id)
+                }
+            }
+        }
+
         // Ensure at least one residence exists (task add button requires it)
         if let residences = TestAccountAPIClient.listResidences(token: session.token),
            residences.isEmpty {
@@ -109,6 +125,9 @@ final class Suite6_ComprehensiveTaskTests: AuthenticatedUITestCase {
             cleaner.trackTask(created.id)
         }
 
+        // Navigate to tasks tab to trigger list refresh and reset scroll position
+        navigateToTasks()
+
         return true
     }