feat(squad): generic game-scoped opaque extension + server fingerprint, atomic in replace_squad tx

migrations/0017_game_entity_ext.sql

@@ -0,0 +1,23 @@
+-- Generic, game-scoped OPAQUE extension storage.
+--
+-- Core persists, versions, associates (to a canonical entity + a server-computed
+-- fingerprint), and enforces generic safety bounds on these bytes — but NEVER
+-- interprets them. A game adapter owns the payload's schema and meaning. This is
+-- how a game keeps wire-only round-trip state (e.g. FIFA 17 squad custom[]/
+-- kicktakers/kitNumber) durable and atomic with its canonical entity without
+-- leaking game-specific columns into generic Core.
+--
+-- Scope key: (game_id, entity_kind, entity_id, namespace). `namespace` is an
+-- opaque adapter key (e.g. "fifa17.squad.v1"); `schema_version` is the adapter's
+-- payload version (distinct from this table's storage schema).
+CREATE TABLE IF NOT EXISTS game_entity_ext (
+    game_id               TEXT    NOT NULL,
+    entity_kind           TEXT    NOT NULL,
+    entity_id             TEXT    NOT NULL,
+    namespace             TEXT    NOT NULL,
+    schema_version        INTEGER NOT NULL,
+    canonical_fingerprint TEXT    NOT NULL,
+    payload               TEXT    NOT NULL,
+    updated_at            TEXT    NOT NULL,
+    PRIMARY KEY (game_id, entity_kind, entity_id, namespace)
+);