Add end-to-end tests for task modification and assignment features

- Implemented tests for editing penalty points and reward costs in `penalty-edit-points.spec.ts` and `reward-edit-cost.spec.ts`.
- Created detailed plans for task activation and assignment scenarios in `task-activated.plan.md` and `task-assignment.plan.md`.
- Added comprehensive test cases for modifying tasks, including editing points for chores, kindness acts, penalties, and rewards in `task-modified.plan.md`.
- Ensured all tests are isolated and run in serial mode to maintain state integrity.

frontend/vue-app/e2e/mode_parent/tasks/penalty-default.spec.ts

@@ -10,6 +10,24 @@ test.describe('Default penalty management', () => {
   test('Convert a default penalty to a user item by editing', async ({ page }) => {
     await page.goto('/parent/tasks/chores')
     await page.click('text=Penalties')
+
+    // Cleanup: delete any leftover 'Fighting (custom)' from a prior run
+    while (
+      (await page
+        .getByText('Fighting (custom)', { exact: true })
+        .locator('..')
+        .locator('button[aria-label="Delete item"]')
+        .count()) > 0
+    ) {
+      await page
+        .getByText('Fighting (custom)', { exact: true })
+        .locator('..')
+        .locator('button[aria-label="Delete item"]')
+        .first()
+        .click()
+      await page.getByRole('button', { name: 'Delete', exact: true }).click()
+    }
+
     // locate default penalty
     await expect(page.locator('text=Fighting')).toBeVisible()
     await expect(