feat(learn): + opens a sheet as Claude's, Camera, Photos and Files, and what goes along in rounded rows

Following the developer's review of 3 Nov 2026 (ADR 0021, D67):

- + below the assistant's field, and below a conversation's follow-up,
  opens "Add to your question" as Claude's "Add to session": three big
  tiles side by side, Camera (where the device takes photos) and Photos
  for an assistant reading images, and Files; below them, in the field, a
  row leading to what goes along, showing how far the assistant looks and
  how many parts are chosen.
- Camera and Photos through image_picker (flutter.dev's own): the camera's
  own app and the system's photo picker, no permission asked on Android, a
  file dialog on the desktop, which has no Camera; photos made at most
  2048 pixels a side, read on the device like any file attached.
- What goes along is chosen in rounded rows, as Claude's Permission, in
  place of radio buttons and chips: how far it looks with a tick, private
  studysets with a switch, the parts each with a tick, a card's image with
  its thumbnail.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/learn/halkyon_learn_flutter/test/support/fake_photo_picker.dart

@@ -0,0 +1,29 @@
+import 'package:halkyon_app/halkyon_app.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/data/photo_picker.dart';
+
+/// A [PhotoPicker] that takes [taken] and picks [picked], noting each ask.
+class FakePhotoPicker() implements PhotoPicker {
+  @override
+  bool hasCamera = true;
+
+  /// What the camera takes next; null as if the person took none.
+  PickedFile? taken;
+
+  /// What the photos picked next are.
+  List<PickedFile> picked = const [];
+
+  /// How often the camera and the photos were asked, in order.
+  final asked = <String>[];
+
+  @override
+  Future<PickedFile?> take() async {
+    asked.add('camera');
+    return taken;
+  }
+
+  @override
+  Future<List<PickedFile>> pick() async {
+    asked.add('photos');
+    return picked;
+  }
+}

apps/learn/halkyon_learn_flutter/test/support/test_dependencies.dart

@@ -24,6 +24,7 @@ import 'package:halkyon_learn_flutter/src/feature/archive/model/import_archive.d
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_files.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/assistant_lookups.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/conversation_repository.dart';
+import 'package:halkyon_learn_flutter/src/feature/assistant/data/photo_picker.dart';
 import 'package:halkyon_learn_flutter/src/feature/assistant/data/web_search.dart';
 import 'package:halkyon_learn_flutter/src/feature/card/data/card_deletions.dart';
 import 'package:halkyon_learn_flutter/src/feature/card/data/card_gateway.dart';
@@ -95,6 +96,7 @@ import 'fake_note_gateway.dart';
 import 'fake_path_answer_gateway.dart';
 import 'fake_pdf_engine.dart';
 import 'fake_pdf_source_gateway.dart';
+import 'fake_photo_picker.dart';
 import 'fake_pomodoro_platform.dart';
 import 'fake_publish_gateway.dart';
 import 'fake_review_gateway.dart';
@@ -172,6 +174,7 @@ Dependencies testDependencies({
   OpenPerson? openPerson,
   WebSearch? webSearch,
   SpeechInput? speech,
+  PhotoPicker? photos,
   JellyfinGateway? jellyfinGateway,
   JellyfinStore? jellyfinStore,
   JellyfinSuggestion? jellyfinSuggestion,
@@ -264,6 +267,7 @@ Dependencies testDependencies({
           deviceSearch: (query) async => false,
         ),
     speech: speech ?? FakeSpeechInput(),
+    photos: photos ?? FakePhotoPicker(),
     jellyfin: JellyfinRepository(
       (device) => jellyfinGateway ?? FakeJellyfinGateway(),
       jellyfinStore ?? MemoryJellyfinStore(),