Task #171: Schedule Edit/View toggle (final fixes)

Add a single global "تحرير/Edit" toggle button to the schedule
toolbar that hides every editing affordance by default and reveals
them only when the user (with edit permission) explicitly opts in.

Affordances now gated behind `effectiveCanMutate = canMutate &&
editMode`:
- "+ Add row" button
- Per-row delete, color swatch, merge trigger, drag grip
- Inline cell editors (EditableCell, TimeRangeCell)
- Column drag-reorder (SortableHeader.dragEnabled)
- Column resize handles
- "+ Add attendee" button AND its pending ghost row

Persistence:
- Toggle state is stored in localStorage under a per-user key
  `em-schedule-edit-mode-v1:<userId>`, so a shared browser cannot
  leak one editor's last toggle into another account that signs
  in. Falls back to view mode when userId is unavailable.
- Always starts in view mode for users without edit permission.

Toggle-off safety:
- EditableCell + TimeRangeCell discard any in-progress draft and
  exit edit mode when their `disabled` / `canMutate` prop flips.
- ScheduleSection clears `pendingAttendee` in a useEffect when
  effectiveCanMutate becomes false, so the ghost "+ Add attendee"
  row unmounts immediately.
- AttendeeFlow also gates the pending render on `canMutate` as
  defense in depth.

i18n: 4 new keys under `executiveMeetings.schedule`
(editToggle / editToggleAria / editToggleOn / editToggleOff)
in both en.json and ar.json.

Tests: tests/executive-meetings-edit-toggle.spec.mjs covers
default-hidden affordances, toggle-on reveal, reload persistence,
and toggle-off re-hide. Cleanup wipes all `em-schedule-edit-mode-v1*`
keys to handle the user-namespaced storage. Full e2e suite (12
tests) passes.

Code review: PASS on the second pass after the per-user key + ghost
row fixes. Pre-existing TS errors in admin.tsx and
use-notifications-socket.ts are codegen drift from earlier tasks
and are not touched by this change.

artifacts/tx-os/tests/executive-meetings-edit-toggle.spec.mjs

@@ -0,0 +1,81 @@
+import { test, expect } from "@playwright/test";
+
+async function loginViaUi(page, username, password) {
+  await page.goto("/login");
+  await page.locator("#username").fill(username);
+  await page.locator("#password").fill(password);
+  await Promise.all([
+    page.waitForURL((url) => !url.pathname.endsWith("/login"), {
+      timeout: 15_000,
+    }),
+    page.locator('form button[type="submit"]').click(),
+  ]);
+}
+
+test("Schedule: Edit toggle hides editing affordances by default and reveals them when on", async ({
+  page,
+}) => {
+  await page.addInitScript(() => {
+    try {
+      window.localStorage.setItem("tx-lang", "en");
+    } catch {
+      /* localStorage may not be ready before navigation */
+    }
+  });
+
+  await loginViaUi(page, "admin", "admin123");
+  // Make sure we always start the test in view mode regardless of any
+  // previously-persisted toggle state from another run. We clear AFTER
+  // login so the cleanup isn't undone by the initScript on every nav.
+  await page.goto("/executive-meetings");
+  // The toggle's storage key is namespaced per-user
+  // (`em-schedule-edit-mode-v1:<userId>`), so we wipe every entry that
+  // starts with the base key to make sure we begin in view mode no
+  // matter who admin's userId resolves to in this run.
+  await page.evaluate(() => {
+    try {
+      const keys = Object.keys(window.localStorage);
+      for (const k of keys) {
+        if (k.startsWith("em-schedule-edit-mode-v1")) {
+          window.localStorage.removeItem(k);
+        }
+      }
+    } catch {
+      /* ignore */
+    }
+  });
+  await page.reload();
+
+  // Toggle is rendered (admin has edit permission), and starts in
+  // pressed=false / view mode.
+  const toggle = page.getByTestId("em-edit-mode-toggle");
+  await expect(toggle).toBeVisible();
+  await expect(toggle).toHaveAttribute("aria-pressed", "false");
+
+  // In view mode the row-level "Add meeting" button must be hidden.
+  await expect(page.getByTestId("em-add-row-button")).toHaveCount(0);
+  // And no row-level overlays (delete, color picker, merge trigger,
+  // grip handle) should exist anywhere in the table.
+  await expect(page.locator('[data-testid^="em-delete-row-"]')).toHaveCount(0);
+  await expect(page.getByTestId("em-row-color-trigger")).toHaveCount(0);
+  await expect(page.locator('[data-testid^="em-merge-trigger-"]')).toHaveCount(0);
+  await expect(page.locator('[data-testid^="em-row-grip-"]')).toHaveCount(0);
+
+  // Flip toggle on. aria-pressed becomes true and the affordances appear.
+  await toggle.click();
+  await expect(toggle).toHaveAttribute("aria-pressed", "true");
+
+  // The "+ Add meeting" row button is back.
+  await expect(page.getByTestId("em-add-row-button")).toBeVisible();
+
+  // Persist + survive a reload: the toggle should still be on.
+  await page.reload();
+  const toggleAfterReload = page.getByTestId("em-edit-mode-toggle");
+  await expect(toggleAfterReload).toHaveAttribute("aria-pressed", "true");
+  await expect(page.getByTestId("em-add-row-button")).toBeVisible();
+
+  // Toggle back off — affordances disappear again.
+  await toggleAfterReload.click();
+  await expect(toggleAfterReload).toHaveAttribute("aria-pressed", "false");
+  await expect(page.getByTestId("em-add-row-button")).toHaveCount(0);
+});