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/fixtures/README.md

@@ -30,9 +30,9 @@ declarations of the entities they use: JMdict is © the Electronic Dictionary
 Research and Development Group, used under its licence, CC BY-SA 4.0
 (<https://www.edrdg.org/edrdg/licence.html>).
 
-`wiktionary-sample.jsonl` holds 29 lines of kaikki.org's Wiktextract data of the
+`wiktionary-sample.jsonl` holds 30 lines of kaikki.org's Wiktextract data of the
 English Wiktionary (the dump of 2026-10-03, read per word from kaikki.org): the
-German Haus, Häuser, Häusern, essen, aß, gegessen and Straße, the Greek σπίτι,
+German Haus, Häuser, Häusern, essen, aß, gegessen, Straße and im, the Greek σπίτι,
 σπιτιού and γράφω, the English house, houses, go and went, the French maison,
 and the Korean 먹다, 집 and 학생, each shortened to the fields the curator reads (no categories,
 etymologies or related words; at most six senses, two examples, 40 forms, two