feat: Claude Code Monitor — lanes, pipelines and a merged workspace

Internal SmartGift build of a Claude Code monitoring dashboard.

Lanes: a durable unit of parallel agent work, one per working directory,
tracked across session restarts. Managed lanes are git worktrees the
dashboard provisions and can reset or remove behind a three-check destroy
guard and a counted preflight; adopted lanes are directories you already
own and are never destroyable.

Pipelines: a lane moves through pipeline stages. A stage the agent declares
with evidence renders green; a stage inferred from the tool-event stream
renders dashed amber and never counts as done. Detection is forward-only
within a 30-minute window, and never writes the declared stage.

Workspace: one page at /run with a lane grid, the selected lane's pipeline,
and a full Claude console behind a disclosure.

server/routes/stats.js

@@ -0,0 +1,45 @@
+/**
+ * @file Express router for stats endpoints, providing aggregated statistics about agents, sessions, events, and WebSocket connections. It queries the database for various counts and statuses, and returns a comprehensive overview in JSON format for frontend display on the dashboard.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const { Router } = require("express");
+const { stmts, db } = require("../db");
+const { getConnectionCount } = require("../websocket");
+const { parseSources } = require("../lib/source-filter");
+const scoped = require("../lib/scoped-stats");
+
+const router = Router();
+
+router.get("/", (req, res) => {
+  // Client sends tz_offset (minutes from getTimezoneOffset(), e.g. 420 for PDT)
+  const rawOffset = parseInt(req.query.tz_offset, 10);
+  const offsetMin = Number.isFinite(rawOffset) ? rawOffset : 0;
+  const toLocal = `${-offsetMin} minutes`; // shift UTC → local
+  const toUTC = `${offsetMin} minutes`; // shift local → UTC
+
+  // Data-scope: when the user restricts to a subset of source machines, compute
+  // every count against that subset; otherwise use the cached prepared stmts.
+  const sources = parseSources(req);
+  const overview = sources ? scoped.statsOverview(db, sources) : stmts.stats.get();
+  const agentsByStatus = sources
+    ? scoped.agentStatusCounts(db, sources)
+    : stmts.agentStatusCounts.all();
+  const sessionsByStatus = sources
+    ? scoped.sessionStatusCounts(db, sources)
+    : stmts.sessionStatusCounts.all();
+
+  const eventsToday = sources
+    ? scoped.countEventsToday(db, sources, toLocal, toUTC)
+    : stmts.countEventsToday.get(toLocal, toUTC);
+
+  res.json({
+    ...overview,
+    events_today: eventsToday?.count ?? 0,
+    ws_connections: getConnectionCount(),
+    agents_by_status: Object.fromEntries(agentsByStatus.map((r) => [r.status, r.count])),
+    sessions_by_status: Object.fromEntries(sessionsByStatus.map((r) => [r.status, r.count])),
+  });
+});
+
+module.exports = router;