Wired the existing exportGlobalThemeOverrideBundle to a real download flow. Export sub-area now shows a reactive button that enables when global overrides exist.
v112.22026-06-10
·AppShell: window listener for theme:exportBundle → JSON blob download
·Filename: lumaweave-overrides-{themeId}-{timestamp}.json (ISO 8601 compact)
·ExportSubArea: useSyncExternalStore on lw:override-change for live enable/disable
·Export nav tab flipped live: true; StubSubArea replaced with ExportSubArea
·i18n: theme.export.{downloadButton,emptyTooltip,scopeHint} added to en.json