fix: never claim 'not in store' while the store state is unknown

A failed/unloaded store snapshot used to be indistinguishable from
a known-empty store, so every missing capability was labelled 'not
in store' the moment the hub or store endpoint was unreachable — a
wrong claim. storeCapabilities is now nullable (null = unknown):
missing caps then get the plain missing chip with an honest
tooltip, no install offer and no not-in-store claim; the analyzer
message says the store cannot be checked right now (EN+DE). Split
and badge covered by new unit + widget tests.

Signed-off-by: flemming-it <sf@flemming.it>

test/missing_modules_badge_test.dart

@@ -25,6 +25,14 @@ void main() {
       final split = splitMissingCaps(['text.extract'], {});
       expect(split.installable, isEmpty);
       expect(split.notInStore, ['text.extract']);
+      expect(split.unclassified, isEmpty);
+    });
+
+    test('null store set (state unknown) classifies nothing', () {
+      final split = splitMissingCaps(['text.extract'], null);
+      expect(split.installable, isEmpty);
+      expect(split.notInStore, isEmpty);
+      expect(split.unclassified, ['text.extract']);
     });
   });
 
@@ -86,6 +94,29 @@ void main() {
       },
     );
 
+    testWidgets('unknown store state offers neither install nor claims', (
+      tester,
+    ) async {
+      await tester.pumpWidget(
+        MaterialApp(
+          home: Scaffold(
+            body: MissingModulesBadge(
+              installable: const [],
+              notInStore: const [],
+              unclassified: const ['text.extract'],
+              strings: const FlowEditorStrings(FlowEditorLocale.en),
+              onInstall: () => fail('no install offer while store unknown'),
+            ),
+          ),
+        ),
+      );
+      expect(find.text('1 module missing'), findsOneWidget);
+      expect(find.text('Install'), findsNothing);
+      expect(find.textContaining('not in store'), findsNothing);
+      final tooltip = tester.widget<Tooltip>(find.byType(Tooltip));
+      expect(tooltip.message, contains('store is not reachable'));
+    });
+
     testWidgets('mixed state renders both chips, install covers store caps', (
       tester,
     ) async {