feat: add safe cross-platform upstream updater (#98)

* feat: add safe upstream update scripts

* fix(updater): use portable PowerShell temp path

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Co-authored-by: Wibias <37517432+Wibias@users.noreply.github.com>

package.json

@@ -79,7 +79,11 @@
     "smoke:live": "node scripts/smoke.mjs --live",
     "capability": "node scripts/capability-smoke.mjs",
     "gauntlet": "node scripts/capability-smoke.mjs --gauntlet",
-    "test:gate": "npm run build --silent && node scripts/test-gate.mjs"
+    "test:gate": "npm run build --silent && node scripts/test-gate.mjs",
+    "update": "node scripts/update.mjs",
+    "update:dry": "node scripts/update.mjs --dry-run",
+    "update:hard": "node scripts/update.mjs --hard",
+    "test:update": "node scripts/test-update.mjs"
   },
   "bin": {
     "tempest": "./dist/cli.js",