Serve subscriptions/listen with a pluggable event bus (SEP-2575) (#3035)

.github/actions/conformance/expected-failures.2026-07-28.yml

@@ -22,7 +22,4 @@
 
 client: []
 
-server:
-  # SEP-2575 subscriptions/listen is not implemented yet; see the matching
-  # entry in expected-failures.yml for the full rationale.
-  - server-stateless
+server: []

.github/actions/conformance/expected-failures.yml

@@ -13,16 +13,6 @@
 client: []
 
 server:
-  # SEP-2575 subscriptions/listen is not implemented yet. The everything-
-  # server's legacy resources/subscribe handlers make it advertise
-  # `resources.subscribe` in server/discover, and as of conformance #372 a
-  # server that advertises a subscription capability but answers
-  # subscriptions/listen with -32601 fails the three listen MUST checks
-  # ("Not testable") instead of skipping them. Remove this entry when the
-  # listen runtime lands. NOTE: while listed, this entry also masks new
-  # failures in the scenario's other 25 (currently passing) checks — the
-  # baseline is per-scenario, not per-check.
-  - server-stateless
   # SEP-2663 (io.modelcontextprotocol/tasks): the SDK does not implement the
   # tasks extension yet. These extension-tagged scenarios are selected only by
   # the bare `--suite all` leg — extension scenarios never match a