feat(host): /api/host CPU/mem/disk/net from /proc

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/host/resources.js

@@ -0,0 +1,42 @@
+// lib/host/resources.js — reads CT 311's own /proc + statfs. Node 22 fs.statfs.
+import { readFile } from 'node:fs/promises';
+import { statfs } from 'node:fs/promises';
+
+async function cpuSample() {
+  const line = (await readFile('/proc/stat', 'utf8')).split('\n')[0]; // "cpu  u n s i ..."
+  const v = line.trim().split(/\s+/).slice(1).map(Number);
+  const idle = v[3] + (v[4] || 0);
+  const total = v.reduce((a, b) => a + b, 0);
+  return { idle, total };
+}
+
+export async function snapshot() {
+  // CPU%: two samples ~100ms apart.
+  const a = await cpuSample();
+  await new Promise(r => setTimeout(r, 100));
+  const b = await cpuSample();
+  const dTotal = b.total - a.total, dIdle = b.idle - a.idle;
+  const cpu_pct = dTotal > 0 ? Math.round((1 - dIdle / dTotal) * 100) : 0;
+
+  // Memory from /proc/meminfo (kB).
+  const mem = Object.fromEntries(
+    (await readFile('/proc/meminfo', 'utf8')).split('\n').filter(Boolean).map(l => {
+      const [k, val] = l.split(':'); return [k.trim(), parseInt(val) * 1024];
+    })
+  );
+  const total = mem.MemTotal, avail = mem.MemAvailable ?? mem.MemFree;
+  const memOut = { total, used: total - avail, pct: Math.round((1 - avail / total) * 100) };
+
+  // Disk for / via statfs.
+  const fs = await statfs('/');
+  const dTotalB = fs.blocks * fs.bsize, dFree = fs.bavail * fs.bsize;
+  const disk = { total: dTotalB, free: dFree, pct: Math.round((1 - dFree / dTotalB) * 100) };
+
+  // Net totals from /proc/net/dev (sum non-lo interfaces).
+  let rx = 0, tx = 0;
+  for (const l of (await readFile('/proc/net/dev', 'utf8')).split('\n')) {
+    const m = l.match(/^\s*([^:]+):\s+(\d+)(?:\s+\d+){7}\s+(\d+)/);
+    if (m && m[1].trim() !== 'lo') { rx += Number(m[2]); tx += Number(m[3]); }
+  }
+  return { cpu_pct, mem: memOut, disk, net: { rx_bytes: rx, tx_bytes: tx }, at: Date.now() };
+}