runtime: add execution concurrency limits

TASKS.md

@@ -2,18 +2,19 @@
 
 ## Current
 
-### `feat/correlation-id-propagation`
+### `feat/runtime-rate-limiting-and-backpressure`
 
 Status: in_progress
 
 DoD:
-- admin-api, mcp-server, runtime, and adapters share a propagated correlation id
-- request-scoped logs can be joined across layers without guessing from timestamps
-- outbound adapter calls include correlation metadata where transport allows it
+- runtime rejects overload deterministically with stable error codes
+- unary, window, session, and async-job execution paths are concurrency-bounded
+- configuration is explicit and documented
+- admin-api and mcp-server use the configured runtime limits
 
 ## Next
 
-- `feat/runtime-rate-limiting-and-backpressure`
+- `feat/distributed-mcp-session-store`
 
 ## Backlog