dawg: build committed dictionary DAWGs (en SOWPODS, ru Scrabble, ru Эрудит)

- cmd/builddict: add -alphabet latin|russian (russian = alphabet.Embedded(LangRu)).
- dictprep/fold_yo.py: fold Ё→Е and de-dup, the Эрудит dictionary prep.
- Makefile: `make dawg` rebuilds dawg/{en_sowpods,ru_scrabble,ru_erudit}.dawg.
- dawg/: committed DAWGs verified by enumeration — 267752 / 83385 / 83343 words.

Makefile

@@ -0,0 +1,28 @@
+# Scrabble-solver build helpers.
+#
+# `make dawg` (re)builds the committed dictionary DAWGs under dawg/ from their word lists:
+#   en_sowpods.dawg  — English SOWPODS (Latin alphabet)
+#   ru_scrabble.dawg — Russian Scrabble nouns (Cyrillic, 33 letters)
+#   ru_erudit.dawg   — Эрудит (the same list with Ё→Е folded and de-duped)
+
+GO        ?= go
+PYTHON    ?= python3
+DAWG_DIR  := dawg
+BUILDDICT := $(GO) run ./cmd/builddict
+
+.PHONY: dawg dawg-en dawg-ru dawg-erudit clean-dawg
+
+dawg: dawg-en dawg-ru dawg-erudit
+
+dawg-en:
+	$(BUILDDICT) -dict dictionaries/english/sowpods.txt -alphabet latin -name en_sowpods -out $(DAWG_DIR)
+
+dawg-ru:
+	$(BUILDDICT) -dict dictprep/russian/scrabble.txt -alphabet russian -name ru_scrabble -out $(DAWG_DIR)
+
+dawg-erudit:
+	$(PYTHON) dictprep/fold_yo.py dictprep/russian/scrabble.txt > /tmp/ru_erudit_words.txt
+	$(BUILDDICT) -dict /tmp/ru_erudit_words.txt -alphabet russian -name ru_erudit -out $(DAWG_DIR)
+
+clean-dawg:
+	rm -f $(DAWG_DIR)/*.dawg