chore: cleanup unused and add unlisted dependencies in packages/a2a-server (#18916)

package-lock.json

@@ -17245,6 +17245,7 @@
         "@google/gemini-cli-core": "file:../core",
         "express": "^5.1.0",
         "fs-extra": "^11.3.0",
+        "strip-json-comments": "^3.1.1",
         "tar": "^7.5.2",
         "uuid": "^13.0.0",
         "winston": "^3.17.0"
@@ -17253,6 +17254,7 @@
         "gemini-cli-a2a-server": "dist/a2a-server.mjs"
       },
       "devDependencies": {
+        "@google/genai": "^1.30.0",
         "@types/express": "^5.0.3",
         "@types/fs-extra": "^11.0.4",
         "@types/supertest": "^6.0.3",