chore: Halkyon Learn moves into apps/learn

Its server, client, app and curator, and the tools that write its
assets (maps, Anki fixtures, icons), as they are; paths are fixed in
the commits that follow.

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_server/test/unit/publish/release_license_test.dart

@@ -0,0 +1,62 @@
+import 'package:halkyon_learn_server/src/publish/release_license.dart';
+import 'package:test/test.dart';
+
+void main() {
+  test('licences that allow passing content on allow publishing', () {
+    for (final license in [
+      'CC0-1.0',
+      'Public domain',
+      'CC-BY-4.0',
+      'CC-BY-SA-3.0-US',
+      'CC-BY-NC-SA-4.0',
+      'CC-BY-ND-4.0',
+      'cc-by-nc-nd-4.0',
+      'ODbL-1.0',
+      'GFDL-1.3-no-invariants-or-later',
+      'GPL-3.0-or-later',
+      'AGPL-3.0-only',
+      'MIT',
+      'Apache-2.0',
+    ]) {
+      expect(allowsPublishing(license), isTrue, reason: license);
+    }
+  });
+
+  test('no licence, all rights reserved, or one not known to be open '
+      "doesn't", () {
+    for (final license in [
+      null,
+      '',
+      ' ',
+      'All Rights Reserved',
+      'GPLv3',
+      'Proprietary',
+      'CC-BY',
+      'CC-SA-1.0',
+    ]) {
+      expect(allowsPublishing(license), isFalse, reason: license);
+    }
+  });
+
+  test('ShareAlike and copyleft licences keep adaptations under them', () {
+    for (final license in [
+      'CC-BY-SA-4.0',
+      'CC-BY-NC-SA-3.0-US',
+      'GPL-3.0-or-later',
+      'GFDL-1.3-only',
+      'ODbL-1.0',
+    ]) {
+      expect(keepsAdaptations(license), isTrue, reason: license);
+    }
+    for (final license in ['CC-BY-4.0', 'CC0-1.0', 'MIT', 'CC-BY-ND-4.0']) {
+      expect(keepsAdaptations(license), isFalse, reason: license);
+    }
+  });
+
+  test('"no derivatives" forbids passing on adaptations', () {
+    expect(forbidsAdaptations('CC-BY-ND-4.0'), isTrue);
+    expect(forbidsAdaptations('CC-BY-NC-ND-3.0-DE'), isTrue);
+    expect(forbidsAdaptations('CC-BY-SA-4.0'), isFalse);
+    expect(forbidsAdaptations('MIT'), isFalse);
+  });
+}

apps/learn/halkyon_learn_server/test/unit/publish/release_repository_test.dart

@@ -0,0 +1,46 @@
+import 'dart:convert';
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:halkyon_learn_server/src/publish/release_repository.dart';
+import 'package:test/test.dart';
+
+void main() {
+  late Directory folder;
+
+  setUp(() async {
+    folder = await Directory.systemTemp.createTemp('release-repository-');
+  });
+  tearDown(() => folder.delete(recursive: true));
+
+  const someone = (name: 'Someone', email: 'someone@example.org');
+
+  test('reads a release of thousands of files back, as large as a '
+      "language's vocabulary, without waiting on git for ever", () async {
+    // git answers each object as it reads its name: once its answers fill
+    // the pipe, it reads no more names until they are read, so they must
+    // be read while the names are still being written.
+    final repository = ReleaseRepository(Directory('${folder.path}/r.git'));
+    Uint8List cardOf(int index) => utf8.encode(
+      jsonEncode({'id': 'card-$index', 'payload': 'x' * 900}),
+    );
+    await repository.release(
+      files: {
+        for (var index = 0; index < 3000; index++)
+          'cards/card-$index.json': () async => cardOf(index),
+      },
+      version: 1,
+      message: 'v1',
+      author: someone,
+      committer: someone,
+      at: DateTime.utc(2026, 10, 16),
+    );
+
+    final read = await repository
+        .readJson(1)
+        .timeout(const Duration(seconds: 30));
+
+    expect(read, hasLength(3000));
+    expect(read['cards/card-42.json'], utf8.decode(cardOf(42)));
+  }, timeout: const Timeout(Duration(minutes: 2)));
+}