#599 fullscreen-exit button: icon only, no text label

In executive-meetings.tsx, the floating exit-fullscreen control was
a pill (`gap-1.5 px-3 py-1.5`) showing both a Minimize2 arrow and
the Arabic/English label "الخروج من ملء الشاشة" / "Exit fullscreen".
User asked for icon only.

Changes:
- Removed the `<span>{t(...)}</span>` label.
- Swapped pill classes for a circular icon button: `inline-flex
  items-center justify-center rounded-full bg-[#0B1E3F] text-white
  w-9 h-9 shadow-lg hover:bg-[#0B1E3F]/90 print:hidden`, keeping the
  same `fixed top-3 end-3 z-50` positioning.
- Bumped the icon to `w-5 h-5` so it reads cleanly on its own.
- Added a `title` attribute (hover tooltip) mirroring the existing
  `aria-label` — screen readers + mouse users still get the
  localised "exit fullscreen" affordance.
- `data-testid="em-fullscreen-exit"` untouched, so existing tests
  keep passing.
- No translation key changes; no change to the enter-fullscreen
  toolbar button at L2958.

Verified `pnpm --filter @workspace/tx-os exec tsc --noEmit` clean.

artifacts/tx-os/src/pages/executive-meetings.tsx

@@ -1040,10 +1040,10 @@ function ExecutiveMeetingsPageInner() {
           onClick={() => setIsFullscreen(false)}
           data-testid="em-fullscreen-exit"
           aria-label={t("executiveMeetings.fullscreen.exit", "Exit fullscreen")}
-          className="fixed top-3 end-3 z-50 inline-flex items-center gap-1.5 rounded-full bg-[#0B1E3F] text-white px-3 py-1.5 text-xs sm:text-sm shadow-lg hover:bg-[#0B1E3F]/90 print:hidden"
+          title={t("executiveMeetings.fullscreen.exit", "Exit fullscreen")}
+          className="fixed top-3 end-3 z-50 inline-flex items-center justify-center rounded-full bg-[#0B1E3F] text-white w-9 h-9 shadow-lg hover:bg-[#0B1E3F]/90 print:hidden"
         >
-          <Minimize2 className="w-4 h-4" />
-          <span>{t("executiveMeetings.fullscreen.exit", "Exit fullscreen")}</span>
+          <Minimize2 className="w-5 h-5" />
         </button>
       )}
       <header