chore: point to SDK with flavor metadata

Author: irstavr

package.json

@@ -48,7 +48,7 @@
   },
   "peerDependencies": {
     "@openfeature/server-sdk": "^1.14.0",
-    "unleash-client": "^6.0.0"
+    "unleash-client": "^6.0.0 || 6.12.0-beta.0"
   },
   "devDependencies": {
     "@biomejs/biome": "2.5.2",
@@ -57,7 +57,7 @@
     "@types/node": "^22.20.0",
     "tsup": "^8.0.0",
     "typescript": "^5.9.3",
-    "unleash-client": "^6.0.0",
+    "unleash-client": "6.12.0-beta.0",
     "vitest": "^4.1.10"
   },
   "publishConfig": {