engine: a Hanja reading answers with the words it begins

hanjaquery matched the reading exactly, so a word was reachable only
once every syllable of it had been typed, and the popup went blank on
the way there.  Measured over map/hanja.dict's 187,304 readings:
95,024 proper prefixes of a word answer with nothing today, and 66,731
of those are the keystroke just before the word completes -- 대한민 is
one, so 대한민국 looks absent until the last key lands.

dictprefix walks the entry at a node before its children, so the
reading's own conversions keep their place and the words follow: 34,441
readings gain candidates and none of the 187,304 has its existing order
changed.  A jamo reading is untouched, since the two keyspaces do not
meet and ㅁ has no children.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

strans.c

@@ -627,13 +627,18 @@ emojiquery(void)
 	selectfirst();
 }
 
-/* The keys typed since Ctrl+H go on composing from the seed. */
+/*
+ * The keys typed since Ctrl+H go on composing from the seed.  A reading
+ * is also the start of the longer words it begins, so its own
+ * conversions come first and theirs follow: 대한 answers 大寒 and, past
+ * them, 大韓民國.
+ */
 static void
 hanjaquery(void)
 {
 	transstr(im.l, &search.seed, &search.raw, &search.text);
 	clearkouho();
-	im.nkouho = dictlookup(getlang(LangHANJA)->dict, &search.text,
+	im.nkouho = dictprefix(getlang(LangHANJA)->dict, &search.text,
 		im.kouho, Maxkouho);
 	selectfirst();
 }