feat(search): suggestions sans doublons + suggestions locales a la frappe

server/suggest.mjs

@@ -0,0 +1,41 @@
+// Suggest helpers (pure, no network, no DB) — shared dedup policy:
+// the same occurrence is only ever returned once (first provider wins).
+
+/** Normalize a suggestion string for dedup comparisons. */
+export function normSuggestKey(s) {
+  return String(s ?? '').trim().toLowerCase().replace(/\s+/g, ' ');
+}
+
+/**
+ * Deduplicate suggestion groups across providers: the same occurrence
+ * (case/whitespace-insensitive) is kept only once, in the first provider
+ * group (registry order). Within a group, order is preserved (first wins).
+ * @param {Record<string, string[]>} groups
+ * @param {string[]} order provider ids in priority order
+ * @returns {Record<string, string[]>} same keys, deduped lists
+ */
+export function dedupeSuggestGroups(groups, order = ['yt', 'dm', 'tw', 'pt', 'od', 'ru']) {
+  const src = groups && typeof groups === 'object' ? groups : {};
+  const seen = new Set();
+  const out = {};
+  const pushList = (pid) => {
+    const list = Array.isArray(src[pid]) ? src[pid] : [];
+    const clean = [];
+    for (const raw of list) {
+      const t = String(raw ?? '').trim();
+      if (!t) continue;
+      const k = normSuggestKey(t);
+      if (seen.has(k)) continue;
+      seen.add(k);
+      clean.push(t);
+    }
+    out[pid] = clean;
+  };
+  for (const pid of order) {
+    if (Object.prototype.hasOwnProperty.call(src, pid)) pushList(pid);
+  }
+  for (const pid of Object.keys(src)) {
+    if (!order.includes(pid)) pushList(pid);
+  }
+  return out;
+}