feat: add SSE event feed for llama-swap api/events

tests/event-feed.test.ts

@@ -0,0 +1,66 @@
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { decodeEvent } from "../src/lib/event-feed";
+import type { SseMessage } from "../src/lib/sse";
+
+test("decodeEvent parses an inflight snapshot", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({
+      type: "inflight",
+      data: JSON.stringify({
+        operation: "snapshot",
+        requests: [{ id: "14", model: "Qwen3.8-27B-NVFP4", req_path: "/v1/chat/completions", elapsed_ms: 165510 }],
+      }),
+    }),
+  };
+  const ev = decodeEvent(msg);
+  assert.ok(ev);
+  assert.equal(ev.type, "inflight");
+  if (ev.type === "inflight") {
+    assert.equal(ev.operation, "snapshot");
+    assert.equal(ev.requests.length, 1);
+    assert.equal(ev.requests[0].model, "Qwen3.8-27B-NVFP4");
+    assert.equal(ev.requests[0].elapsed_ms, 165510);
+  }
+});
+
+test("decodeEvent parses an inflight add with a singular request field", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({
+      type: "inflight",
+      data: JSON.stringify({ operation: "add", request: { id: "9", model: "A" } }),
+    }),
+  };
+  const ev = decodeEvent(msg);
+  assert.ok(ev && ev.type === "inflight");
+  if (ev && ev.type === "inflight") {
+    assert.equal(ev.operation, "add");
+    assert.equal(ev.requests[0].model, "A");
+  }
+});
+
+test("decodeEvent parses modelStatus", () => {
+  const msg: SseMessage = {
+    event: "message",
+    data: JSON.stringify({
+      type: "modelStatus",
+      data: JSON.stringify([
+        { id: "DeepSeek-V4-Flash-0731", state: "ready" },
+        { id: "Qwen3.8-27B-NVFP4", state: "stopped" },
+      ]),
+    }),
+  };
+  const ev = decodeEvent(msg);
+  assert.ok(ev && ev.type === "modelStatus");
+  if (ev && ev.type === "modelStatus") {
+    assert.equal(ev.models.length, 2);
+    assert.equal(ev.models[0].state, "ready");
+  }
+});
+
+test("decodeEvent returns null for unrelated or malformed events", () => {
+  assert.equal(decodeEvent({ event: "message", data: JSON.stringify({ type: "logData", data: "{}" }) }), null);
+  assert.equal(decodeEvent({ event: "message", data: "not json" }), null);
+});