fix(curator): contractions are words of their own

Wiktionary tags a contraction as an abbreviation and an alternative of
its first word (im: in + dem), so German's im, zum and ins, which every
subtitle has, were neither entries nor found as forms. A contraction is
now an entry of its own, as text writes it.

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

halkyon_learn_curator/test/wiktionary_test.dart

@@ -140,6 +140,8 @@ void main() {
         (essen['textKeys']! as List).cast<String>(),
         containsAll(['isst', 'aß', 'gegessen']),
       );
+      // A contraction is a word of its own: im, of in and dem.
+      expect(ids, contains('im/contraction'));
       // Typed with `ss`.
       expect(
         (entryOf('wiktionary-de-en.jsonl.gz', 'Straße/noun')['looseKeys']!
@@ -246,8 +248,14 @@ void main() {
       for (final line in linesOf('wiktionary-de-en.jsonl.gz').skip(1))
         (line['headword'], line['rank']! as int, line['labels']),
     ]..sort((a, b) => a.$2.compareTo(b.$2));
-    expect(ranked.first.$1, 'Haus');
-    expect(ranked.first.$3, ['common']);
+    expect(
+      [
+        for (final (word, _, _) in ranked)
+          if (['im', 'Haus', 'Straße'].contains(word)) word,
+      ],
+      ['im', 'Haus', 'Straße'],
+    );
+    expect(ranked.firstWhere((each) => each.$1 == 'Haus').$3, ['common']);
   });
 
   group('folding', () {