Accept value-only DKIM TXT pastes for Email DNS

Allow v=DKIM1… pastes without a zone name by taking an optional
selector hint so Arvan/Cloudflare still get the right _domainkey record.

src/mail-dns/mail-dns.ts

@@ -11,13 +11,29 @@ export type MailDkimKey = {
   text: string;
 };
 
+/** Bare selector, or `name._domainkey` / `name._domainkey.example.com.` */
+export function normalizeDkimSelector(raw: string | undefined | null): string | null {
+  if (raw == null) return null;
+  let input = raw.trim().replace(/^"+|"+$/g, '').trim();
+  if (!input) return null;
+
+  const hostMatch = input.match(/^([a-z0-9][a-z0-9-]*)\._domainkey(?:\.|$)/i);
+  if (hostMatch) return hostMatch[1].toLowerCase();
+
+  if (/^[a-z0-9][a-z0-9-]*$/i.test(input)) return input.toLowerCase();
+  return null;
+}
+
 export function parseDkimPaste(
   raw: string,
   expectedKind: 'ed25519' | 'rsa',
+  selectorHint?: string,
 ): MailDkimKey {
   const input = raw.trim();
   if (!input) {
-    throw new Error(`Paste the ${expectedKind} DKIM line from Stalwart.`);
+    throw new Error(
+      `Paste the ${expectedKind} DKIM TXT value (v=DKIM1; …) or the full Stalwart zone line.`,
+    );
   }
 
   const quoted = [...input.matchAll(/"([^"]*)"/g)].map((match) => match[1]).join('');
@@ -29,7 +45,7 @@ export function parseDkimPaste(
   text = text.replace(/^"+|"+$/g, '').replace(/\s+/g, ' ').replace(/[.\s]+$/g, '').trim();
   if (!/^v=DKIM1/i.test(text)) {
     throw new Error(
-      `Could not find a v=DKIM1 value in the ${expectedKind} field. Paste the Stalwart zone line.`,
+      `Could not find a v=DKIM1 value in the ${expectedKind} field. Paste the TXT value or Stalwart zone line.`,
     );
   }
 
@@ -45,14 +61,16 @@ export function parseDkimPaste(
   }
 
   const nameMatch = compact.match(/([a-z0-9][a-z0-9-]*)\._domainkey/i);
-  if (!nameMatch) {
+  const selector =
+    (nameMatch ? nameMatch[1].toLowerCase() : null) || normalizeDkimSelector(selectorHint);
+  if (!selector) {
     throw new Error(
-      'Include the selector name (for example v1-ed25519-20260831._domainkey) from the Stalwart zone file.',
+      'Could not find a DKIM selector. Enter the selector (for example v1-ed25519-20260901), or paste a zone line that includes …._domainkey.',
     );
   }
 
   return {
-    selector: nameMatch[1].toLowerCase(),
+    selector,
     text,
   };
 }