feat: import session sheet redesign and metadata-gen filter

Filter persisted metadata-generation sessions out of the import list so
existing on-disk entries stop polluting it for users.

Rename the surface to "Import session" everywhere, swap the bespoke
filter pills for SegmentedControl with provider icons, drop the trailing
provider label on rows (icon is enough), tighten padding, and align the
row icon with the segmented control's left edge.

packages/app/src/components/ui/segmented-control.tsx

@@ -145,6 +145,7 @@ const styles = StyleSheet.create((theme) => ({
     maxWidth: "100%",
     backgroundColor: theme.colors.surface2,
     borderRadius: theme.borderRadius.lg,
+    gap: 2,
   },
   containerSm: {
     padding: 2,