chore(deps): declare the node 22.12 floor the bump introduces

Review follow-up. electron-builder 26.15.3 pulls @electron/rebuild 4, whose
engines are `node >=22.12.0` (master was on @electron/rebuild 3, `>=12.13.0`),
and the root postinstall runs `electron-builder install-app-deps` on every
install. CI already runs Node 22, but nothing in the repo said so — no
`engines`, no `.nvmrc` — so a contributor on an older Node would have hit a
confusing rebuild failure instead of a clear one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

docs/architecture/workspace-shell.md

@@ -312,6 +312,10 @@ Toolchain notes for the Electron 41 upgrade:
 2. The pnpm override `node-abi@3.85.0 -> 3.92.0` is required so
    `@electron/rebuild` (via `electron-builder install-app-deps`) can map
    Electron 41 to its ABI.
+3. Local development needs **Node >= 22.12**, declared in `engines`.
+   `electron-builder` 26.15.3 pulls `@electron/rebuild` 4, which sets that
+   floor, and the root `postinstall` runs `install-app-deps` on every
+   `pnpm install`. CI already runs Node 22.
 
 Known caveats:
 

package.json

@@ -70,6 +70,9 @@
         "build": "nx build electron-backend"
     },
     "private": true,
+    "engines": {
+        "node": ">=22.12.0"
+    },
     "packageManager": "pnpm@10.33.0+sha512.10568bb4a6afb58c9eb3630da90cc9516417abebd3fabbe6739f0ae795728da1491e9db5a544c76ad8eb7570f5c4bb3d6c637b2cb41bfdcdb47fa823c8649319",
     "dependencies": {
         "@angular/animations": "21.2.17",