polish(detail): TODO review — calendar intro, drop abundance, collapse seed-saving

From the owner's TODO.org review of the shipped features:
- Crop calendar now says the months are YOUR notes: a hint line in the
  editor (cropCalendar.editorHint) and a caption under the 'this month'
  screen (calendar.selfNote) — it read as if the app knew when to sow.
- Dropped the 'how much I have' (abundance) input + display: it competed
  with the lot quantity as a second 'how much'. Removed from the lot sheet
  and the lot summary; the DB column + backup/CSV/catalog plumbing stay
  dormant (no destructive migration). offer_status carries 'do I share'.
- Seed-saving guidance moved into a collapsed expander (detail.seedSaving)
  — reference facts about the species shouldn't sit open among the
  grower's own records; opt-in depth, per progressive disclosure.
- Condition checks already live behind the collapsed 'advanced' expander
  (seed lots only) — left as the discreet power-user surface.

Tests: dropped the obsolete abundance→share nudge test; the seed-saving
section test now expands before asserting. analyze clean; suites green.

apps/app_seeds/test/ui/seed_saving_section_test.dart

@@ -1,3 +1,4 @@
+import 'package:flutter/widgets.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:tane/data/seed_saving_catalog.dart';
 import 'package:tane/db/database.dart';
@@ -36,7 +37,14 @@ void main() {
   testWidgets('shows the seed-saving section for a known family', (tester) async {
     await pumpDetailFor(tester, 'Solanaceae');
 
+    // The section is a collapsed expander — its title shows, its body doesn't
+    // until opened.
     expect(find.text('Saving its seed'), findsOneWidget);
+    expect(find.textContaining('Self-pollinating'), findsNothing);
+
+    await tester.tap(find.byKey(const Key('detail.seedSaving')));
+    await tester.pumpAndSettle();
+
     // The pollination line is a Text.rich (label + value), so match the run.
     expect(find.textContaining('Self-pollinating'), findsOneWidget);
     expect(find.text('Easy'), findsOneWidget); // the difficulty pill