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/codec.test.ts

@@ -36,7 +36,7 @@ describe('codec', () => {
   });
 
   it('encodes a SubmitPlayRequest with alphabet indices (Stage 13)', () => {
-    setAlphabet('english', [
+    setAlphabet('scrabble_en', [
       { index: 0, letter: 'a', value: 1 },
       { index: 1, letter: 'b', value: 3 },
     ]);
@@ -48,7 +48,7 @@ describe('codec', () => {
         { row: 7, col: 7, letter: 'A', blank: false },
         { row: 7, col: 8, letter: 'B', blank: true },
       ],
-      'english',
+      'scrabble_en',
     );
     const r = fb.SubmitPlayRequest.getRootAsSubmitPlayRequest(new ByteBuffer(buf));
     expect(r.gameId()).toBe('g1');
@@ -95,7 +95,7 @@ describe('codec', () => {
     const seat = fb.SeatView.endSeatView(b);
     const seats = fb.GameView.createSeatsVector(b, [seat]);
     const id = b.createString('g1');
-    const variant = b.createString('english');
+    const variant = b.createString('scrabble_en');
     const dv = b.createString('v1');
     const status = b.createString('active');
     const er = b.createString('');
@@ -242,7 +242,7 @@ describe('codec', () => {
     const invitees = fb.Invitation.createInviteesVector(b, [invitee]);
 
     const id = b.createString('i-1');
-    const variant = b.createString('english');
+    const variant = b.createString('scrabble_en');
     const dropout = b.createString('remove');
     const status = b.createString('pending');
     const gid = b.createString('');
@@ -264,7 +264,7 @@ describe('codec', () => {
     expect(inv.inviter).toEqual({ accountId: 'u-1', displayName: 'Me' });
     expect(inv.invitees).toHaveLength(1);
     expect(inv.invitees[0]).toEqual({ accountId: 'inv-1', displayName: 'Friend', seat: 1, response: 'pending' });
-    expect(inv.variant).toBe('english');
+    expect(inv.variant).toBe('scrabble_en');
   });
 });
 
@@ -273,12 +273,12 @@ describe('codec', () => {
 // the whole table), so they are independent of order.
 describe('codec — alphabet on the wire (Stage 13)', () => {
   it('encodes an ExchangeRequest as alphabet indices, blank as the sentinel', () => {
-    setAlphabet('english', [
+    setAlphabet('scrabble_en', [
       { index: 0, letter: 'a', value: 1 },
       { index: 1, letter: 'b', value: 3 },
     ]);
     const r = fb.ExchangeRequest.getRootAsExchangeRequest(
-      new ByteBuffer(encodeExchange('g1', ['A', '?'], 'english')),
+      new ByteBuffer(encodeExchange('g1', ['A', '?'], 'scrabble_en')),
     );
     expect(r.tilesLength()).toBe(2);
     expect(r.tiles(0)).toBe(0);
@@ -286,13 +286,13 @@ describe('codec — alphabet on the wire (Stage 13)', () => {
   });
 
   it('encodes a CheckWordRequest as alphabet indices', () => {
-    setAlphabet('english', [
+    setAlphabet('scrabble_en', [
       { index: 0, letter: 'a', value: 1 },
       { index: 2, letter: 'c', value: 3 },
       { index: 19, letter: 't', value: 1 },
     ]);
     const r = fb.CheckWordRequest.getRootAsCheckWordRequest(
-      new ByteBuffer(encodeCheckWord('g1', 'CAT', 'english')),
+      new ByteBuffer(encodeCheckWord('g1', 'CAT', 'scrabble_en')),
     );
     expect(r.wordLength()).toBe(3);
     expect([r.word(0), r.word(1), r.word(2)]).toEqual([2, 0, 19]);
@@ -330,7 +330,7 @@ describe('codec — alphabet on the wire (Stage 13)', () => {
     fb.StateView.addAlphabet(b, alpha);
     b.finish(fb.StateView.endStateView(b));
 
-    // No GameView on the buffer, so decode falls back to the default variant 'english';
+    // No GameView on the buffer, so decode falls back to the default variant 'scrabble_en';
     // the embedded table is cached under it and the rack [0, blank] decodes to letters.
     const sv = decodeStateView(b.asUint8Array());
     expect(sv.rack).toEqual(['A', '?']);