feat: add window execution to runtime

TASKS.md

@@ -2,19 +2,20 @@
 
 ## Current
 
-### `feat/stream-session-store`
+### `feat/runtime-window-mode`
 
 Status: completed
 
 DoD:
-- persistent tables exist for `stream_sessions` and `async_jobs`
-- registry supports create/get/update/close/list/cleanup for both stores
-- invalid state transitions are rejected explicitly
-- migration and storage tests cover lifecycle and cleanup
+- runtime exposes bounded `window` execution
+- item and byte limits are enforced
+- `window_complete`, `truncated`, `has_more` are returned
+- aggregation and redaction are covered by tests
+- unary execution remains intact
 
 ## Next
 
-- `feat/runtime-window-mode`
+- `feat/rest-sse-adapter`
 
 ## Backlog