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

tests/lib/watcher.test.ts

@@ -0,0 +1,45 @@
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import fs from 'node:fs/promises';
+import os from 'node:os';
+import path from 'node:path';
+
+import { IssuesEventBus } from '../../src/lib/realtime';
+import { IssuesWatchManager } from '../../src/lib/watcher';
+
+test('IssuesWatchManager startWatch is idempotent per project', async () => {
+  const bus = new IssuesEventBus();
+  const manager = new IssuesWatchManager({ eventBus: bus, debounceMs: 20 });
+
+  manager.startWatch('C:/Repo/One');
+  manager.startWatch('c:\\repo\\one');
+
+  assert.equal(manager.getWatchedProjectCount(), 1);
+  await manager.stopAll();
+});
+
+test('IssuesWatchManager emits event after file change in watched .beads path', async () => {
+  const root = await fs.mkdtemp(path.join(os.tmpdir(), 'beadboard-watch-'));
+  const beadsDir = path.join(root, '.beads');
+  const issuesPath = path.join(beadsDir, 'issues.jsonl');
+  await fs.mkdir(beadsDir, { recursive: true });
+  await fs.writeFile(issuesPath, '', 'utf8');
+
+  const bus = new IssuesEventBus();
+  const manager = new IssuesWatchManager({ eventBus: bus, debounceMs: 40 });
+
+  const events: string[] = [];
+  const stop = bus.subscribe((event) => {
+    events.push(event.projectRoot);
+  });
+
+  manager.startWatch(root);
+
+  await fs.writeFile(issuesPath, `${JSON.stringify({ id: 'bb-1', title: 'watch' })}\n`, 'utf8');
+  await new Promise((resolve) => setTimeout(resolve, 220));
+
+  stop();
+  await manager.stopAll();
+
+  assert.equal(events.length >= 1, true);
+});