feat(data-explorer): infer Mongo dialect instead of asking for it

The source dropdown already says "MongoDB", so the form's second
mongodb/documentdb/cosmosdb/ferretdb picker read as a duplicate question.
Removed it and derived dbType from the connection string.

dbType stays load-bearing: normalizeConnectionString appends
retryWrites=false for DocumentDB and Cosmos, which reject the driver's
default and would otherwise fail writes silently. Both are identifiable by
their managed hostnames, which is what detectDbType matches (already
covered by lib/__tests__/nosql-dialects.test.ts). When detection cannot
tell, the connection's saved dbType is kept, so an explicit FerretDB
choice from an older build survives an edit.

The connection-string placeholder still follows the inferred dialect.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: itsmeakhil

apps/desktop-ui/src/components/data-explorer/adapters/mongodb.tsx

@@ -50,7 +50,7 @@ import {
 } from "@/lib/nosql-error-sanitizer";
 import {
     DB_DIALECTS,
-    DB_TYPE_ORDER,
+    detectDbType,
     normalizeConnectionString,
     type DbType,
 } from "@/lib/nosql-dialects";
@@ -137,7 +137,23 @@ function MongoConnectionForm({
     const [color, setColor] = useState<string | null>(initial.color ?? null);
     const [readOnly, setReadOnly] = useState(initial.readOnly ?? false);
     const [connectionString, setConnectionString] = useState(initial.config.connectionString);
-    const [dbType, setDbType] = useState<DbType>(initial.config.dbType);
+
+    /**
+     * Inferred from the connection string, not picked by the user — the source
+     * dropdown already said "MongoDB" and asking again read as a duplicate.
+     *
+     * `dbType` is still load-bearing: `normalizeConnectionString` appends
+     * `retryWrites=false` for DocumentDB and Cosmos, which reject the driver's
+     * default and would otherwise fail writes silently. Both are identifiable
+     * by their managed hostnames, which is exactly what `detectDbType` matches.
+     * It falls back to "mongodb" when it cannot tell, so keep whatever the
+     * connection was saved with in that case — an explicit FerretDB choice from
+     * an older build then survives an edit.
+     */
+    const dbType = useMemo<DbType>(() => {
+        const detected = detectDbType(connectionString);
+        return detected === "mongodb" ? initial.config.dbType : detected;
+    }, [connectionString, initial.config.dbType]);
 
     function handleSubmit(e: React.FormEvent) {
         e.preventDefault();
@@ -168,28 +184,6 @@ function MongoConnectionForm({
                 />
             </div>
 
-            <div className="space-y-2">
-                <Label>{t("dbType")}</Label>
-                <div className="grid grid-cols-2 gap-2">
-                    {DB_TYPE_ORDER.map((type) => (
-                        <button
-                            key={type}
-                            type="button"
-                            onClick={() => setDbType(type)}
-                            disabled={saving}
-                            className={cn(
-                                "rounded-lg border px-3 py-2 text-left text-sm font-medium transition-colors",
-                                dbType === type
-                                    ? "border-primary bg-primary/5 ring-1 ring-primary/20"
-                                    : "border-border bg-background/50 hover:border-primary/30"
-                            )}
-                        >
-                            {DB_DIALECTS[type].label}
-                        </button>
-                    ))}
-                </div>
-            </div>
-
             <div className="space-y-2">
                 <Label htmlFor="mongo-connection-string">{t("connectionString")}</Label>
                 <Input