feat(search): add Xquik as an X search provider

Xquik needs a GET request with x-api-key auth and a tweets envelope
normalizer, neither of which the generic search fallback provides. Adds a
dedicated request builder and normalizer, cursor pagination passthrough,
result-based credit usage reporting, and a validateUrl probe so key
validation hits the no-charge credits endpoint.

open-sse/providers/registry/xquik.js

@@ -0,0 +1,35 @@
+export default {
+  id: "xquik",
+  alias: "xquik",
+  display: {
+    name: "Xquik",
+    icon: "tag",
+    color: "#5C3327",
+    textIcon: "XQ",
+    website: "https://docs.xquik.com/api-reference/x/search-tweets",
+    notice: {
+      apiKeyUrl: "https://xquik.com",
+      text: "Searches public X posts. Billing uses 1 Xquik credit per returned post."
+    }
+  },
+  category: "apikey",
+  authType: "apikey",
+  serviceKinds: [
+    "webSearch"
+  ],
+  searchConfig: {
+    baseUrl: "https://xquik.com/api/v1/x/tweets/search",
+    validateUrl: "https://xquik.com/api/v1/credits",
+    method: "GET",
+    authType: "apikey",
+    authHeader: "x-api-key",
+    searchTypes: [
+      "x"
+    ],
+    defaultMaxResults: 5,
+    maxMaxResults: 100,
+    timeoutMs: 10000,
+    cacheTTLMs: 60000,
+    creditsPerResult: 1
+  }
+};