Fix stale contact suggestions reopening

hide() did not invalidate in-flight search requests. Clearing
the input or picking a contact while a request was pending let
the old response re-render and pop the suggestion list back
open. Bump requestSeq in hide() so every dismissal retires
pending responses.

Add a Vitest + jsdom harness with black-box tests for the
invitee widget, covering the stale-response race both on
field clear and on contact pick.

package.json

@@ -0,0 +1,11 @@
+{
+  "private": true,
+  "description": "JS test harness for the atocal frontend scripts",
+  "scripts": {
+    "test:js": "vitest run"
+  },
+  "devDependencies": {
+    "jsdom": "^26.1.0",
+    "vitest": "^3.2.4"
+  }
+}