feat(system-info): include disk usage in health output

docs/plans/state.json

@@ -5612,6 +5612,18 @@
         "docs/plans/state.json"
       ],
       "test_status": "pnpm test:run src/gateway/handlers/agent.test.ts + pnpm typecheck passing"
+    },
+    "system-info-disk-usage-reporting": {
+      "status": "completed",
+      "date": "2026-02-19",
+      "updated": "2026-02-19",
+      "summary": "Extended `system.info` tool output to include disk usage metrics (path, total/free/used, and used percentage) so machine health summaries include storage headroom in addition to memory.",
+      "files_modified": [
+        "src/tools/builtin/system-info.ts",
+        "src/tools/builtin/system-info.test.ts",
+        "docs/plans/state.json"
+      ],
+      "test_status": "pnpm test:run src/tools/builtin/system-info.test.ts + pnpm typecheck passing"
     }
   },
   "overall_progress": {

src/tools/builtin/system-info.test.ts

@@ -42,6 +42,7 @@ describe('system.info tool', () => {
       'Node.js:',
       'Uptime:',
       'Memory Total:',
+      'Disk',
     ];
 
     for (const field of expectedFields) {

src/tools/builtin/system-info.ts

@@ -1,4 +1,5 @@
 import os from 'os';
+import { statfsSync } from 'fs';
 import type { Tool, ToolResult } from '../types.js';
 
 function formatUptime(seconds: number): string {
@@ -12,6 +13,34 @@ function formatBytes(bytes: number): string {
   return (bytes / (1024 * 1024 * 1024)).toFixed(2) + ' GB';
 }
 
+function getDiskUsageSummary(): string[] {
+  try {
+    const rootPath = process.platform === 'win32' ? process.cwd().slice(0, 3) : '/';
+    const stat = statfsSync(rootPath);
+    const blockSize = typeof stat.bsize === 'number' ? stat.bsize : Number(stat.bsize);
+    const totalBlocks = typeof stat.blocks === 'number' ? stat.blocks : Number(stat.blocks);
+    const freeBlocks = typeof stat.bavail === 'number' ? stat.bavail : Number(stat.bavail);
+
+    if (!Number.isFinite(blockSize) || !Number.isFinite(totalBlocks) || !Number.isFinite(freeBlocks)) {
+      return ['Disk:          unavailable'];
+    }
+
+    const totalBytes = totalBlocks * blockSize;
+    const freeBytes = freeBlocks * blockSize;
+    const usedBytes = Math.max(0, totalBytes - freeBytes);
+    const usedPct = totalBytes > 0 ? (usedBytes / totalBytes) * 100 : 0;
+
+    return [
+      `Disk Path:     ${rootPath}`,
+      `Disk Total:    ${formatBytes(totalBytes)}`,
+      `Disk Free:     ${formatBytes(freeBytes)}`,
+      `Disk Used:     ${formatBytes(usedBytes)} (${usedPct.toFixed(1)}%)`,
+    ];
+  } catch {
+    return ['Disk:          unavailable'];
+  }
+}
+
 export const systemInfoTool: Tool = {
   name: 'system.info',
   description: 'Get current system information including date, time, hostname, OS, platform, architecture, uptime, Node.js version, and memory usage.',
@@ -52,6 +81,7 @@ export const systemInfoTool: Tool = {
         `Node.js:       ${process.version}`,
         `Memory Total:  ${formatBytes(totalMem)}`,
         `Memory Free:   ${formatBytes(freeMem)}`,
+        ...getDiskUsageSummary(),
         `Working Dir:   ${process.cwd()}`,
       ];