change database schema: include winrate

install/database_schema.sql

@@ -381,6 +381,7 @@ CREATE TABLE endgames (
     rank          SMALLINT, /* 0 for clue actions */
     enumerator    BIGINT NOT NULL CHECK (enumerator >= 0),
     denominator   BIGINT  NOT NULL CHECK (denominator > 0),
+    chance        REAL GENERATED ALWAYS AS (CAST(enumerator AS REAL) / denominator) STORED,
     PRIMARY KEY (game_id, turn, action_type, suit_index, rank)
 );