docs: sync completed backpressure track

TASKS.md

@@ -2,19 +2,20 @@
 
 ## Current
 
-### `feat/runtime-rate-limiting-and-backpressure`
+### `feat/distributed-mcp-session-store`
 
 Status: in_progress
 
 DoD:
-- runtime concurrency limits reject overload deterministically
-- mcp-server transport requests are throttled on ingress across `POST`, `GET`, and `DELETE`
-- streaming poll pressure is bounded for stream sessions and async jobs
-- admin-api ingress requests are throttled with stable `429` behavior
+- transport sessions are stored behind a shared store abstraction
+- mcp-server no longer depends directly on process-local session storage implementation
+- in-memory session store remains available for tests and local fallback
+- production mcp-server uses a Postgres-backed transport session store
+- expired transport sessions are evicted on read and no longer leak indefinitely
 
 ## Next
 
-- `feat/distributed-mcp-session-store`
+- `feat/runtime-rate-limiting-and-backpressure`
 
 ## Backlog