Add todo_md_staleness State Hub context resolver

Supports daily TODO.md stale-review ActivityDefinition via
GET /repos/todo-md-staleness.

src/activity_core/context_resolvers/state_hub.py

@@ -100,6 +100,8 @@ class StateHubContextResolver(ContextResolver):
             return _fetch_json(f"/state/domain/{domain}")
         if query == "repo_sbom_status":
             return _repo_sbom_status(params)
+        if query == "todo_md_staleness":
+            return _todo_md_staleness(params)
         if query == "state_summary":
             return _fetch_json("/state/summary")
         if query == "next_steps":
@@ -374,6 +376,26 @@ def _repo_sbom_status(params: dict[str, Any]) -> dict[str, Any]:
     return {}
 
 
+def _todo_md_staleness(params: dict[str, Any]) -> dict[str, Any]:
+    """Resolve TODO.md staleness from State Hub.
+
+    Bulk mode (default): GET /repos/todo-md-staleness?stale_days=N
+    Returns stale repos under `repos` plus summary fields for rule matching.
+    """
+    stale_days = params.get("stale_days", 6)
+    try:
+        stale_days = int(stale_days)
+    except (TypeError, ValueError):
+        stale_days = 6
+    payload = _fetch_json("/repos/todo-md-staleness", {"stale_days": stale_days})
+    if not isinstance(payload, dict) or not payload:
+        return {}
+    repos = payload.get("repos")
+    if not isinstance(repos, list):
+        return {}
+    return payload
+
+
 def _sbom_status_entry(repo_slug: str, last_sbom_at: Any) -> dict[str, Any]:
     age_days, has_sbom, normalised = _sbom_age_days(last_sbom_at)
     return {