Patch up some missing tests and fix+test channel add not clearing on channel submission without add-another checked

frontend/package-lock.json

@@ -38,6 +38,7 @@
         "@eslint/js": "^9.17.0",
         "@testing-library/jest-dom": "^6.6.0",
         "@testing-library/react": "^16.0.0",
+        "@testing-library/user-event": "^14.6.1",
         "@types/d3-force": "^3.0.10",
         "@types/leaflet": "^1.9.21",
         "@types/node": "^25.0.3",
@@ -1593,6 +1594,20 @@
         }
       }
     },
+    "node_modules/@testing-library/user-event": {
+      "version": "14.6.1",
+      "resolved": "https://registry.npmjs.org/@testing-library/user-event/-/user-event-14.6.1.tgz",
+      "integrity": "sha512-vq7fv0rnt+QTXgPxr5Hjc210p6YKq2kmdziLgnsZGgLJ9e6VAShx1pACLuRjd/AS/sr7phAR58OIIpf0LlmQNw==",
+      "dev": true,
+      "license": "MIT",
+      "engines": {
+        "node": ">=12",
+        "npm": ">=6"
+      },
+      "peerDependencies": {
+        "@testing-library/dom": ">=7.21.4"
+      }
+    },
     "node_modules/@tweenjs/tween.js": {
       "version": "23.1.3",
       "resolved": "https://registry.npmjs.org/@tweenjs/tween.js/-/tween.js-23.1.3.tgz",