chore: pin engines.node to 24.x (was >=22.12.0)

Aligns learn-the-far's package.json engines with .nvmrc (24) and the fleet
Node standard so the declared floor can't drift below the major everything
actually runs on. No runtime change: .nvmrc and CI already resolve to 24.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jsolly

package.json

@@ -3,7 +3,7 @@
   "type": "module",
   "version": "0.0.1",
   "engines": {
-    "node": ">=22.12.0"
+    "node": "24.x"
   },
   "scripts": {
     "dev": "astro dev",