nodes: store and show host disk free; warn when low (node-26#41)

Checkin now carries disk_free_bytes/disk_total_bytes. Stored on the node doc
(not overwritten by older nodes that don't send them). Node page shows a Disk
row; node cards warn amber under 15% free, red under 5% or 2 GB. A full disk
stopped node-002 recording for 17 days while it showed Online.

Frontend unverified locally (no Node, #207); CI build typechecks.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

drb-frontend/app/nodes/[id]/page.tsx

@@ -16,6 +16,7 @@ import { MachineOutputNotice } from "@/components/ui/MachineOutputNotice";
 import { useAuth } from "@/components/AuthProvider";
 import { c2api } from "@/lib/c2api";
 import { errorMessage } from "@/lib/c2error";
+import { diskState, DISK_TEXT_CLASS } from "@/lib/nodeDisk";
 import type { NodeRecord } from "@/lib/types";
 
 function ApprovalBadge({ status }: { status: string | null }) {
@@ -218,6 +219,17 @@ export default function NodeDetailPage() {
             <span className="text-ink">{value}</span>
           </div>
         ))}
+        {(() => {
+          const disk = diskState(node);
+          return (
+            <div className="flex justify-between px-4 py-2.5">
+              <span className="text-ink-muted">Disk</span>
+              <span className={disk ? DISK_TEXT_CLASS[disk.level] : "text-ink-muted"}>
+                {disk ? `${disk.level !== "ok" ? "⚠ " : ""}${disk.label}` : "not reported (node software too old)"}
+              </span>
+            </div>
+          );
+        })()}
         <div className="flex justify-between px-4 py-2.5">
           <span className="text-ink-muted">Approval</span>
           <ApprovalBadge status={node.approval_status ?? null} />

drb-frontend/components/NodeCard.tsx

@@ -1,6 +1,7 @@
 import Link from "next/link";
 import { StatusBadge } from "@/components/StatusBadge";
 import type { NodeRecord, SystemRecord } from "@/lib/types";
+import { diskState } from "@/lib/nodeDisk";
 
 interface Props {
   node: NodeRecord;
@@ -45,6 +46,15 @@ export function NodeCard({ node, system, linkToDetail = true }: Props) {
             <span className="text-ink-2">{lastSeen}</span>
           </div>
         </div>
+        {(() => {
+          const disk = diskState(node);
+          if (!disk || disk.level === "ok") return null;
+          return (
+            <div className={`mt-3 text-xs font-mono border-t border-line pt-2 ${disk.level === "critical" ? "text-sev-major" : "text-sev-moderate"}`}>
+              ⚠ Disk {disk.level === "critical" ? "nearly full" : "low"}: {disk.label}
+            </div>
+          );
+        })()}
         {!node.configured && (
           <div className="mt-3 text-xs text-indigo-400 font-mono border-t border-line pt-2">
             ⚠ Needs configuration

drb-frontend/lib/nodeDisk.ts

@@ -0,0 +1,39 @@
+import type { NodeRecord } from "@/lib/types";
+
+// Free disk on the node's host (node-26#41). A full disk stopped node-002
+// recording for 17 days while every surface still showed it Online, so low
+// space is flagged wherever a node is shown.
+
+export type DiskLevel = "ok" | "low" | "critical";
+
+export interface DiskState {
+  level: DiskLevel;
+  freePct: number;
+  label: string; // e.g. "43.2 GB free of 98 GB (44%)"
+}
+
+const LOW_PCT = 15;
+const CRITICAL_PCT = 5;
+const CRITICAL_BYTES = 2 * 1024 ** 3; // a 2 GB floor regardless of disk size
+
+function gb(bytes: number): string {
+  const v = bytes / 1024 ** 3;
+  return `${v >= 10 ? v.toFixed(0) : v.toFixed(1)} GB`;
+}
+
+/** null when the node has never reported (older node software). */
+export function diskState(node: Pick<NodeRecord, "disk_free_bytes" | "disk_total_bytes">): DiskState | null {
+  const free = node.disk_free_bytes;
+  const total = node.disk_total_bytes;
+  if (free == null || !total) return null;
+  const freePct = Math.max(0, Math.min(100, (free / total) * 100));
+  const level: DiskLevel =
+    freePct < CRITICAL_PCT || free < CRITICAL_BYTES ? "critical" : freePct < LOW_PCT ? "low" : "ok";
+  return { level, freePct, label: `${gb(free)} free of ${gb(total)} (${Math.round(freePct)}%)` };
+}
+
+export const DISK_TEXT_CLASS: Record<DiskLevel, string> = {
+  ok: "text-ink-2",
+  low: "text-sev-moderate",
+  critical: "text-sev-major",
+};

drb-frontend/lib/types.ts

@@ -82,6 +82,9 @@ export interface NodeRecord {
   /** The dongle OP25 is actually using, per the node. */
   op25_sdr_serial?: string | null;
   sdr_count?: number | null; // null = never reported
+  /** Host disk the node records to (node-26#41); null/absent = not reported. */
+  disk_free_bytes?: number | null;
+  disk_total_bytes?: number | null;
   /** node-26#24: conventional channels from the last checkin; [] on a trunked system. */
   radio_channels?: RadioChannel[] | null;
   enforce_override_timeout?: boolean;