feat(app): hint isolation distance when sowing a cross-pollinating crop

One passive line in the batch story after a 'sown today' tap — 'this
species crosses, grow it ~400 m from others' — sourced from the bundled
seed-saving guidance (family default + species override). Selfers get
nothing: the trap is recording isolation religiously for beans where it
never mattered. No input fields, no schema change.

apps/app_seeds/test/ui/lot_history_sheet_test.dart

@@ -1,7 +1,9 @@
 import 'package:flutter/material.dart';
 import 'package:flutter_test/flutter_test.dart';
+import 'package:tane/data/seed_saving_catalog.dart';
 import 'package:tane/db/database.dart';
 import 'package:tane/db/enums.dart';
+import 'package:tane/domain/seed_saving.dart';
 
 import '../support/test_support.dart';
 
@@ -9,7 +11,10 @@ void main() {
   late AppDatabase db;
 
   setUp(() => db = newTestDatabase());
-  tearDown(() => db.close());
+  tearDown(() {
+    SeedSavingCatalog.data = null;
+    return db.close();
+  });
 
   testWidgets('the lot tile opens the batch story, closed by its origin', (
     tester,
@@ -153,6 +158,52 @@ void main() {
     await disposeTree(tester);
   });
 
+  testWidgets('sowing a crosser drops the isolation hint; a selfer gets '
+      'nothing', (tester) async {
+    SeedSavingCatalog.data = SeedSavingData(
+      families: {
+        'Cucurbitaceae': const SeedSavingGuide(
+          pollination: Pollination.cross,
+          isolationMinM: 400,
+        ),
+        'Solanaceae': const SeedSavingGuide(
+          pollination: Pollination.self,
+          isolationMinM: 3,
+        ),
+      },
+      taxa: const {},
+    );
+    final repo = newTestRepository(db);
+
+    Future<void> sowAndCheck(String category, {required bool hinted}) async {
+      final id = await repo.addQuickVariety(label: 'x-$category');
+      await repo.updateVariety(id: id, label: 'x-$category', category: category);
+      final lotId = await repo.addLot(varietyId: id);
+      await tester.pumpWidget(
+        wrapDetail(
+          repository: repo,
+          varietyId: id,
+          species: newTestSpeciesRepository(db),
+        ),
+      );
+      await tester.pumpAndSettle();
+      await tester.tap(find.byKey(Key('lot.history.$lotId')));
+      await tester.pumpAndSettle();
+      await tester.tap(find.byKey(const Key('history.sowToday')));
+      await tester.pumpAndSettle();
+      expect(
+        find.byKey(const Key('history.isolationHint')),
+        hinted ? findsOneWidget : findsNothing,
+      );
+      await disposeTree(tester);
+    }
+
+    // The family drives it: squash (crosses, 400 m) hints; tomato does not.
+    await sowAndCheck('Cucurbitaceae', hinted: true);
+    expect(find.textContaining('400'), findsNothing); // tree disposed
+    await sowAndCheck('Solanaceae', hinted: false);
+  });
+
   testWidgets('a plant lot offers harvest but not sowing', (tester) async {
     final repo = newTestRepository(db);
     final id = await repo.addQuickVariety(label: 'Rosemary');