feat(ru): drop abbreviations from the Russian noun list

The list leaked abbreviations two ways: an OpenCorpora noun tagged Abbr without
Fixd (the declinable acronym ОГВЗ) slipped past the Abbr+Fixd seed filter, and the
РАН «(сокр.)» words (вуз, нэп, колхоз, гост, …) were kept on purpose by the old
policy.

Drop every abbreviation instead. A final pass in ru_stage2.py removes a word when
the orthographic note marks it «(сокр.)» (is_abbrev_note) or when every OpenCorpora
noun reading carries Abbr (oc_abbr_only — also the declinable огвз/заз the seed
filter missed). Homographs with a plain-noun reading survive (ваза «ВАЗ», рис).
Lexicalised words are rescued via manual_confirm.txt (колхоз, совхоз, рация,
спецназ, эсминец, дзот, дот, прораб, токамак, тэн, … and под — a real noun OC knows
only as ПОД); the bound prefix гос is vetoed in manual_reject.txt.

108 words removed from ru_scrabble / ru_erudit; en_sowpods unchanged. tools/README
documents the policy and that libmorph is required for a faithful rebuild.

sources/scrabble_ru/manual_confirm.txt

@@ -133,3 +133,31 @@
 флеш
 флешмобер
 шиноремонт
+военкор
+дзот
+дисбат
+дот
+завгар
+иняз
+каско
+колхоз
+линкор
+морпех
+научпоп
+прораб
+рация
+санбат
+совхоз
+сопромат
+спецназ
+спецхран
+старлей
+старпом
+твэл
+теормех
+токамак
+тэн
+чермет
+эсминец
+юннат
+под