backport: phase-5 cleanup — apply pending deferrals, test_coverage green

Adds the one N-risk deferral (transport:streamable-http:stateless-restrictions) that
phase-4 wave 2 logged in cant-express-v1.md but did not apply to the manifest. The other
three v1-API-gap deferrals (roots:list-changed, resources:templates:pagination,
client-auth:authorize:offline-access-consent) were already applied by their Y-risk
sequential-lane batches.

test_deferral_reasons_cite_existing_paths was already green (no v2-only paths cited).

Full suite: 524 pass / 0 fail. 67 deferred entries (4 v1-API-gap).

Author: maxisbey

tests/interaction/_requirements.py

@@ -1798,6 +1798,12 @@ def __post_init__(self) -> None:
             "result, because there is no session to call back through."
         ),
         transports=("streamable-http",),
+        deferred=(
+            "Not expressible via the v1 public API: v1 stateless mode has no guard on server-initiated "
+            "requests; the request is sent, the response arrives at a fresh stateless transport instance "
+            "and is dropped as an unknown request id, and the handler waits forever. The only observable "
+            "outcome is a hang, which is not pinnable without a time-based wait."
+        ),
     ),
     "transport:streamable-http:unrelated-messages": Requirement(
         source=f"{SPEC_BASE_URL}/basic/transports#streamable-http",