feat(statehub): add offline write buffer relay

tests/test_edge_outbox.py

@@ -0,0 +1,51 @@
+from api.edge.outbox import OutboxStore, PayloadRejected
+from api.services.write_idempotency import route_class_for
+
+
+def test_route_classifier_matches_safe_writes():
+    assert route_class_for("POST", "/progress/") == "append"
+    assert route_class_for("PATCH", "/tasks/abc") == "replace"
+    assert route_class_for("DELETE", "/tasks/abc") is None
+
+
+def test_outbox_scrubs_secret_fields_and_tracks_status(tmp_path):
+    store = OutboxStore(tmp_path / "outbox.sqlite3")
+    envelope = store.enqueue(
+        method="POST",
+        path="/progress/",
+        body={"summary": "offline", "password": "secret", "tokens_in": 12},
+        source_agent="pytest",
+        source_host="host-a",
+    )
+
+    assert envelope.status == "queued"
+    assert envelope.route_class == "append"
+    assert envelope.body["password"] == "[redacted]"
+    assert envelope.body["tokens_in"] == 12
+    assert store.summary()["pending_count"] == 1
+
+    store.mark_acked(envelope.id, response_status=201, response_body={"id": "central"})
+    acked = store.get(envelope.id)
+    assert acked.status == "acked"
+    assert acked.response_body == {"id": "central"}
+    assert store.summary()["pending_count"] == 0
+
+
+def test_outbox_rejects_non_queueable_routes(tmp_path):
+    store = OutboxStore(tmp_path / "outbox.sqlite3")
+    try:
+        store.enqueue(method="DELETE", path="/tasks/abc", body={})
+    except PayloadRejected as exc:
+        assert "not queueable" in str(exc)
+    else:
+        raise AssertionError("DELETE should not be queueable")
+
+
+def test_replace_writes_coalesce_superseded_queued_envelopes(tmp_path):
+    store = OutboxStore(tmp_path / "outbox.sqlite3")
+    first = store.enqueue(method="PATCH", path="/tasks/task-1", body={"status": "progress"})
+    second = store.enqueue(method="PATCH", path="/tasks/task-1", body={"status": "done"})
+
+    assert store.get(first.id).status == "cancelled"
+    assert store.get(second.id).status == "queued"
+    assert len(store.due()) == 1