fix: resolve merge conflict markers in composer.lock

The merge of 1.8.x into feat-mongodb left unresolved conflict markers
in composer.lock, breaking all CI checks. Resolved in favor of
feat-mongodb values (minimum-stability: dev, prefer-stable: true)
to match composer.json.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

composer.lock

@@ -8989,15 +8989,9 @@
         }
     ],
     "aliases": [],
-<<<<<<< feat-mongodb
     "minimum-stability": "dev",
     "stability-flags": {},
     "prefer-stable": true,
-=======
-    "minimum-stability": "stable",
-    "stability-flags": {},
-    "prefer-stable": false,
->>>>>>> 1.8.x
     "prefer-lowest": false,
     "platform": {
         "php": ">=8.3.0",