Address CoPilot review

- ``_deferred_cases`` in ``_run_fixture_028``: dict[str, str] →
  set[str]. The case-level skip uses ``continue`` (not
  ``pytest.skip``) so the reason values had nowhere to surface;
  rationale stays in the per-block comment above the set.
- ``_deferral.py`` docstring: drop the awkward escaped
  pluralization (``\\s`` rendered as a literal ``\s``) in favor
  of plain prose: "it executes ``continue`` inside an async loop".

Author: chris-colinsky

tests/conformance/_deferral.py

@@ -12,8 +12,8 @@
 
 The case-level skip inside ``_run_fixture_028`` in
 ``test_observability.py`` deliberately doesn't use this helper — it
-``continue``\\s inside an async loop iterating sub-cases of a single
-fixture rather than skipping the outer pytest test.
+executes ``continue`` inside an async loop iterating sub-cases of a
+single fixture rather than skipping the outer pytest test.
 """
 
 from __future__ import annotations

tests/conformance/test_observability.py

@@ -895,20 +895,19 @@ async def _run_fixture_028(spec: Mapping[str, Any]) -> None:
     # Case-level deferrals for fixture 028. The spec extends the
     # fixture with new negative-control cases as new reserved keys
     # land in §3.4; impl-side coverage for those cases lands in the
-    # PR that implements the corresponding key reservation.
-    _deferred_cases: dict[str, str] = {
+    # PR that implements the corresponding key reservation. Stored as
+    # a set since the skip is a ``continue`` (no ``pytest.skip``
+    # reason surface); rationale lives in the per-block comment above
+    # each name.
+    _deferred_cases: set[str] = {
         # Proposal 0052 (implementation attribution, spec v0.44.0)
         # extends the reserved-set 24 → 26 names with
         # ``implementation_name`` / ``implementation_version``.
         # Coverage lands in PR 3 of the v0.12.0 cycle alongside the
         # ``openarmature.implementation.*`` invocation-span attribute
         # emission.
-        "rejects_reserved_oa_name_implementation_name": (
-            "Proposal 0052 implementation attribution; lands in PR 3 of v0.12.0"
-        ),
-        "rejects_reserved_oa_name_implementation_version": (
-            "Proposal 0052 implementation attribution; lands in PR 3 of v0.12.0"
-        ),
+        "rejects_reserved_oa_name_implementation_name",
+        "rejects_reserved_oa_name_implementation_version",
     }
     cases = cast("list[dict[str, Any]]", spec["cases"])
     for case in cases: