update

doc/core/cache/features.md

@@ -0,0 +1,5 @@
+- cache
+	- shared read-store / cache client (Redis today)
+	- backend writes, frontend reads
+	- apps keep the cache in sync via event handlers (projectors), not the core client
+	- room for growth: CacheProvider abstraction so the read-store becomes swappable

doc/core/cache/specs.md

@@ -0,0 +1 @@
+- cache.py