feat(ui): show the changed-files count badge on the Git rail surface

Replaces the plain activity dot on the context panel rail's Git button with
a numeric badge of the changed-files count from the git store status, so the
count is visible at a glance without opening the Git surface. Large counts
cap at 99+ to keep the pill within the 36px button. The badge is reflected
in the button's accessible label and the hover tooltip.

Fixes #2364

packages/ui/src/lib/i18n/messages/pl.ts

@@ -1419,6 +1419,8 @@ export const dict: Record<I18nKey, string> = {
   'contextPanel.editorEmpty.description': 'Wybierz plik z drzewa, aby rozpocząć edycję.',
   'contextRail.surface.editor.description': 'Edytuj pliki projektu',
   'contextRail.surface.git.description': 'Commity, gałęzie i pull requesty',
+  'contextRail.surface.git.changesCountAria': '{label}, {count} zmienionych plików',
+  'contextRail.surface.git.changesCountTooltip': '{count} zmienionych plików',
   'contextRail.surface.terminal.description': 'Wbudowany terminal',
   'contextRail.surface.diff.description': 'Przeglądaj bieżące zmiany',
   'contextPanel.mode.walkthrough': 'Przewodnik',