feat: decode activity SSE events and expose tracker total

tests/event-feed.test.ts

@@ -117,3 +117,12 @@ test("decodeEvent handles inflight with a non-array requests field and no reques
     assert.deepEqual(ev.requests, []);
   }
 });
+
+test("decodeEvent parses an activity event with an id", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({ type: "activity", data: JSON.stringify({ id: 817 }) }),
+  };
+  const ev = decodeEvent(msg);
+  assert.deepEqual(ev, { type: "activity", id: 817 });
+});

tests/inflight-tracker.test.ts

@@ -63,3 +63,13 @@ test("modelStatus normalizes states", () => {
   assert.equal(tracker.state("D"), "stopped");
   assert.equal(tracker.state("missing"), undefined);
 });
+
+test("total sums in-flight requests across all models", () => {
+  const tracker = new InflightTracker();
+  assert.equal(tracker.total(), 0);
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "1" }, { model: "B", id: "2" }] });
+  tracker.apply({ type: "inflight", operation: "add", requests: [{ model: "A", id: "3" }] });
+  assert.equal(tracker.total(), 3);
+  tracker.apply({ type: "inflight", operation: "remove", id: "1" });
+  assert.equal(tracker.total(), 2);
+});