R1: schema & naming reset — squash migrations, rename variants

Squash the 12 goose migrations into one 00001_baseline.sql (there is no prod
data; verified schema-identical to the chain via a pg_dump diff + the green
integration suite) and rename the game-variant labels
english/russian_scrabble/erudit -> scrabble_en/scrabble_ru/erudit_ru across the
backend, the FlatBuffers wire values and the UI.

dawg filenames and the Go enum identifiers are unchanged; the i18n display keys
are kept. Adds PRERELEASE.md (the R1-R7 pre-release tracker), linked from
CLAUDE.md. Contour DB wipe and the scrabble-dictionary tidy are follow-ups.

ui/src/lib/alphabet.test.ts

@@ -12,37 +12,37 @@ import {
 // The cache module is per-file-isolated by vitest, so only what these tests seed exists.
 describe('alphabet cache (Stage 13)', () => {
   it('upper-cases letters for display and maps indices and values case-insensitively', () => {
-    setAlphabet('english', [
+    setAlphabet('scrabble_en', [
       { index: 0, letter: 'a', value: 1 },
       { index: 16, letter: 'q', value: 10 },
     ]);
-    expect(hasAlphabet('english')).toBe(true);
-    expect(letterForIndex('english', 0)).toBe('A');
-    expect(letterForIndex('english', 16)).toBe('Q');
-    expect(indexForLetter('english', 'a')).toBe(0);
-    expect(indexForLetter('english', 'Q')).toBe(16);
-    expect(valueForLetter('english', 'a')).toBe(1);
-    expect(valueForLetter('english', 'Q')).toBe(10);
+    expect(hasAlphabet('scrabble_en')).toBe(true);
+    expect(letterForIndex('scrabble_en', 0)).toBe('A');
+    expect(letterForIndex('scrabble_en', 16)).toBe('Q');
+    expect(indexForLetter('scrabble_en', 'a')).toBe(0);
+    expect(indexForLetter('scrabble_en', 'Q')).toBe(16);
+    expect(valueForLetter('scrabble_en', 'a')).toBe(1);
+    expect(valueForLetter('scrabble_en', 'Q')).toBe(10);
   });
 
   it('handles the blank sentinel and unknown letters/indices', () => {
-    setAlphabet('english', [{ index: 0, letter: 'a', value: 1 }]);
-    expect(letterForIndex('english', BLANK_INDEX)).toBe('?');
-    expect(indexForLetter('english', '?')).toBe(BLANK_INDEX);
-    expect(valueForLetter('english', '?')).toBe(0);
-    expect(letterForIndex('english', 99)).toBe(''); // out of range
-    expect(valueForLetter('english', 'Z')).toBe(0); // not in this alphabet
-    expect(() => indexForLetter('english', 'Z')).toThrow();
+    setAlphabet('scrabble_en', [{ index: 0, letter: 'a', value: 1 }]);
+    expect(letterForIndex('scrabble_en', BLANK_INDEX)).toBe('?');
+    expect(indexForLetter('scrabble_en', '?')).toBe(BLANK_INDEX);
+    expect(valueForLetter('scrabble_en', '?')).toBe(0);
+    expect(letterForIndex('scrabble_en', 99)).toBe(''); // out of range
+    expect(valueForLetter('scrabble_en', 'Z')).toBe(0); // not in this alphabet
+    expect(() => indexForLetter('scrabble_en', 'Z')).toThrow();
   });
 
   it('lists the alphabet for the blank chooser and is empty for an uncached variant', () => {
-    setAlphabet('english', [
+    setAlphabet('scrabble_en', [
       { index: 0, letter: 'a', value: 1 },
       { index: 1, letter: 'b', value: 3 },
     ]);
-    expect(alphabetLetters('english')).toEqual(['A', 'B']);
-    expect(hasAlphabet('erudit')).toBe(false);
-    expect(alphabetLetters('erudit')).toEqual([]);
-    expect(valueForLetter('erudit', 'A')).toBe(0);
+    expect(alphabetLetters('scrabble_en')).toEqual(['A', 'B']);
+    expect(hasAlphabet('erudit_ru')).toBe(false);
+    expect(alphabetLetters('erudit_ru')).toEqual([]);
+    expect(valueForLetter('erudit_ru', 'A')).toBe(0);
   });
 });