fix: v2.5.1 — plugin npm runs no longer depend on PATH (Windows update failure)

A Windows self-update failed at "bootstrap": 'npm.cmd' is not recognized.
The update chain runs with the dashboard server's environment, whose PATH
need not reach npm.cmd, and the bootstrap looked npm up through cmd.exe
(shell: true, which also printed DEP0190).

- npmCommand() in scripts/plugin-bootstrap.js runs the npm bundled with the
  running node (npm-cli.js beside process.execPath, Windows and Unix
  layouts) with no shell, and puts that node's directory first on PATH (kept
  under the env's own Path/PATH key) so npm scripts find the same node; npm
  on PATH only when that node ships none
- Used by the runtime install, the UI build (plugin-open.js) and the
  doctor's npm row (plugin-doctor.js)

package-lock.json

@@ -1,12 +1,12 @@
 {
   "name": "agenthub",
-  "version": "2.5.0",
+  "version": "2.5.1",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "agenthub",
-      "version": "2.5.0",
+      "version": "2.5.1",
       "hasInstallScript": true,
       "license": "UNLICENSED",
       "dependencies": {