Add Core Hub production stabilization scheduled checks

Introduce the core-hub context resolver stabilization_check query, State Hub
progress summaries, activity-definition projections, and unit tests for the
CORE-WP-0007 post-cutover window.

tests/test_core_hub_context_resolver.py

@@ -0,0 +1,98 @@
+from __future__ import annotations
+
+from datetime import datetime, timezone
+from typing import Any
+
+import httpx
+
+from activity_core.context_resolvers.core_hub import CoreHubContextResolver
+
+
+class DummyResponse:
+    def __init__(self, payload: Any, status_code: int = 200) -> None:
+        self._payload = payload
+        self.status_code = status_code
+        self.text = str(payload)
+
+    def json(self) -> Any:
+        return self._payload
+
+
+class DummyClient:
+    def __init__(self, responses: dict[str, tuple[Any, int]]) -> None:
+        self._responses = responses
+
+    def __enter__(self) -> DummyClient:
+        return self
+
+    def __exit__(self, *args: Any) -> None:
+        return None
+
+    def get(self, path: str) -> DummyResponse:
+        payload, status = self._responses.get(
+            path,
+            ({}, 404),
+        )
+        return DummyResponse(payload, status)
+
+
+def test_core_hub_stabilization_check_passes(monkeypatch) -> None:
+    widget_types = [{"slug": f"type-{index}"} for index in range(26)]
+    responses = {
+        "/healthz": ({}, 200),
+        "/readyz": ({}, 200),
+        "/api/v2/widget-types": (widget_types, 200),
+        "/api/v2/hubs": ({}, 401),
+    }
+    fixed_now = datetime(2026, 7, 7, 10, 0, tzinfo=timezone.utc)
+    monkeypatch.setattr(httpx, "Client", lambda **kwargs: DummyClient(responses))
+    monkeypatch.setattr(
+        "activity_core.context_resolvers.core_hub._utc_now",
+        lambda: fixed_now,
+    )
+
+    result = CoreHubContextResolver().resolve("stabilization_check", None, {})
+
+    assert result["overall_pass"] is True
+    assert result["skipped"] is False
+    assert result["checks"]["widget_types_count"]["pass"] is True
+    assert result["checks"]["api_v2_hubs"]["pass"] is True
+
+
+def test_core_hub_stabilization_check_skips_outside_window(monkeypatch) -> None:
+    fixed_now = datetime(2026, 7, 12, 10, 0, tzinfo=timezone.utc)
+    monkeypatch.setattr(
+        "activity_core.context_resolvers.core_hub._utc_now",
+        lambda: fixed_now,
+    )
+
+    result = CoreHubContextResolver().resolve("stabilization_check", None, {})
+
+    assert result["skipped"] is True
+    assert result["reason"] == "outside_stabilization_window"
+
+
+def test_core_hub_stabilization_closeout_raises_on_failure(monkeypatch) -> None:
+    responses = {
+        "/healthz": ({}, 500),
+        "/readyz": ({}, 200),
+        "/api/v2/widget-types": ([], 200),
+        "/api/v2/hubs": ({}, 401),
+    }
+    fixed_now = datetime(2026, 7, 7, 10, 0, tzinfo=timezone.utc)
+    monkeypatch.setattr(httpx, "Client", lambda **kwargs: DummyClient(responses))
+    monkeypatch.setattr(
+        "activity_core.context_resolvers.core_hub._utc_now",
+        lambda: fixed_now,
+    )
+
+    try:
+        CoreHubContextResolver().resolve(
+            "stabilization_check",
+            None,
+            {"closeout": True},
+        )
+    except RuntimeError as exc:
+        assert "closeout failed" in str(exc)
+    else:
+        raise AssertionError("expected closeout failure")