alert: keep meeting reminder buttons clickable while a Dialog is open

Task #478. When the upcoming-meeting reminder ("الاجتماع التالي")
appeared on top of an open note thread dialog, the user could not
tap "تأجيل" / "تم" / × / "تفاصيل". The buttons looked enabled and
the popup sat above the dialog overlay (`z-[60]` over `z-50`), but
nothing happened on click.

Root cause: Radix `Dialog` is modal by default and its scroll-lock
helper (`react-remove-scroll`) sets `pointer-events: none` on the
document body while open. The meeting alert is portaled to body and
inherited that, silently swallowing all clicks.

Fix: in `artifacts/tx-os/src/components/executive-meetings/upcoming-
meeting-alert.tsx`, add `pointer-events-auto` to the floating panel's
className so it explicitly opts back in to receiving pointer events.
Buttons inside inherit auto from the panel. Inline comment added
referencing #478 and the Radix scroll-lock behavior.

No change to the shared `Dialog` primitive, no other tokens or
components touched. Existing `#282` behavior (hide alert while its
own postpone modal is open) is preserved.

Verified:
- `tsc --noEmit` clean.
- `notes-thread-dialog.spec.mjs` passes (no regression in the
  scenario that surfaced the bug).

artifacts/tx-os/src/components/executive-meetings/upcoming-meeting-alert.tsx

@@ -533,7 +533,16 @@ export function UpcomingMeetingAlert() {
         // other dialogs/toasts are unaffected. The panel reappears
         // automatically when the modal closes (if the alert is still
         // valid for the current time window).
-        className={`fixed z-[60] w-[min(380px,calc(100vw-32px))] rounded-lg shadow-xl ${
+        // #478: `pointer-events-auto` keeps the alert's buttons clickable
+        // even while a Radix `Dialog` is open elsewhere in the app (e.g.
+        // the notes thread dialog). Radix dialogs ship with
+        // `react-remove-scroll`, which sets `pointer-events: none` on
+        // the document body — anything portaled outside the dialog
+        // (including this fixed alert at `z-[60]`) inherits that and
+        // silently swallows clicks. Forcing pointer-events back to auto
+        // here lets the user act on the reminder without having to
+        // close the unrelated dialog first.
+        className={`pointer-events-auto fixed z-[60] w-[min(380px,calc(100vw-32px))] rounded-lg shadow-xl ${
           postponeOpen ? "hidden" : ""
         } ${enterAnim ? "scale-100 opacity-100" : "scale-95 opacity-0"}`}
         aria-hidden={postponeOpen ? true : undefined}