fix: add trailing slash to publishConfig registry URL

@semantic-release/npm@13 compares publishConfig.registry against
its internal OFFICIAL_REGISTRY constant using strict equality.
The constant has a trailing slash; without it, OIDC token exchange
is silently skipped.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: manuelbieh

package.json

@@ -22,7 +22,7 @@
     "es"
   ],
   "publishConfig": {
-    "registry": "https://registry.npmjs.org",
+    "registry": "https://registry.npmjs.org/",
     "access": "public",
     "provenance": true
   },