[match] do not allow crossplay between 2023 and 2025

apps/rooms/migrations/0012_room_instance_version.sql

@@ -0,0 +1,24 @@
+-- The client build a room instance is running, so matchmaking only ever puts players
+-- on the SAME build into one session. Two builds sharing a Photon room disagree about
+-- how the scene and its objects serialize, so a 2023 client and a 2025 one in the same
+-- instance is a broken room rather than a mixed one — and there is nothing to notice it
+-- by afterwards, since each side simply fails to see what the other spawned.
+--
+-- The value is the `rn.ver` claim of the token whose matchmake CREATED the instance
+-- (the match worker stamps it; see resolveRoomInstance), and the joinable-instance
+-- search filters on it. A room busy with players on another build therefore reads as
+-- empty and the joiner gets a fresh instance beside them.
+--
+-- Rows written before this column existed have no `$.gameVersion`, so `game_version`
+-- is NULL and they match no build at all. That is deliberate: an unknown build is not
+-- a build to place someone into, and an instance is only ever a live session — once it
+-- empties, deleteEmptyRoomInstances retires it and nothing is left carrying a NULL.
+--
+-- A virtual generated column like the rest of the table (the value lives in the `data`
+-- blob); no index — the search is already keyed on the indexed `room_id`.
+--
+-- Generated from packages/domain/src/room-instance-db.ts (ROOM_INSTANCE_SCHEMA_DDL) —
+-- keep in sync.
+
+ALTER TABLE room_instance
+  ADD COLUMN game_version TEXT GENERATED ALWAYS AS (json_extract(data, '$.gameVersion')) VIRTUAL;