Add realtime watcher+SSE transport with tests and lock-retry read path

tests/lib/realtime.test.ts

@@ -0,0 +1,46 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+
+import { IssuesEventBus, toSseFrame } from '../../src/lib/realtime';
+
+test('IssuesEventBus emits monotonically increasing IDs', () => {
+  const bus = new IssuesEventBus();
+  const seen: number[] = [];
+  const unsubscribe = bus.subscribe((event) => seen.push(event.id));
+
+  bus.emit('C:/Repo/One');
+  bus.emit('C:/Repo/One');
+  unsubscribe();
+
+  assert.deepEqual(seen, [1, 2]);
+});
+
+test('IssuesEventBus filters by project root', () => {
+  const bus = new IssuesEventBus();
+  const one: number[] = [];
+  const two: number[] = [];
+  const stopOne = bus.subscribe((event) => one.push(event.id), { projectRoot: 'C:/Repo/One' });
+  const stopTwo = bus.subscribe((event) => two.push(event.id), { projectRoot: 'D:/Repo/Two' });
+
+  bus.emit('c:\\repo\\one');
+  bus.emit('D:/Repo/Two');
+
+  stopOne();
+  stopTwo();
+
+  assert.deepEqual(one, [1]);
+  assert.deepEqual(two, [2]);
+});
+
+test('toSseFrame includes id, event name, and data payload', () => {
+  const frame = toSseFrame({
+    id: 9,
+    projectRoot: 'C:\\Repo\\One',
+    kind: 'changed',
+    at: '2026-02-12T01:00:00.000Z',
+  });
+
+  assert.equal(frame.includes('id: 9'), true);
+  assert.equal(frame.includes('event: issues'), true);
+  assert.equal(frame.includes('"projectRoot":"C:\\\\Repo\\\\One"'), true);
+});