fix(builder): deterministic ids for NumberCounter + form-relay marker

Two components of the det-id bug class were missed in the earlier migration:
NumberCounter's wrapper/counter ids and count-up script, and the shared
form-relay-wiring fid (used by ContactForm/FormContainer). Both used
Math.random() for exported HTML ids, breaking caching/diffing across exports.

Migrate both to scopeId(nodeId, fallbackSeed, prefix), threading nodeId
through NumberCounter.toHtml and relayFormWiring (via ContactForm.toHtml and
FormContainer.toHtml, both now passing nodeId as their 3rd arg).

craft/src/utils/form-relay-wiring.test.ts

@@ -0,0 +1,38 @@
+import { describe, test, expect } from 'vitest';
+import { relayFormWiring } from './form-relay-wiring';
+
+describe('relayFormWiring deterministic + unique fid (thread node id, no Math.random)', () => {
+  test('no recipient: no relay, no marker, no fid needed', () => {
+    const wiring = relayFormWiring(undefined, undefined, '/legacy', 'node-1');
+    expect(wiring.useRelay).toBe(false);
+    expect(wiring.marker).toBe('');
+  });
+
+  test('same node id -> identical marker + placeholder ids across two calls (deterministic)', () => {
+    const w1 = relayFormWiring('a@b.com', '/thx', undefined, 'node-form1');
+    const w2 = relayFormWiring('a@b.com', '/thx', undefined, 'node-form1');
+    expect(w1.marker).toBe(w2.marker);
+    expect(w1.actionAttr).toBe(w2.actionAttr);
+  });
+
+  test('marker id and placeholder id always match each other', () => {
+    const w = relayFormWiring('a@b.com', '/thx', undefined, 'node-form1');
+    const mid = w.marker.match(/id="([^"]+)"/)![1];
+    expect(w.actionAttr).toBe(`__WHP_FORM_ACTION__${mid}__`);
+  });
+
+  test('different node ids -> different fids (no collision)', () => {
+    const w1 = relayFormWiring('a@b.com', '/thx', undefined, 'node-form1');
+    const w2 = relayFormWiring('a@b.com', '/thx', undefined, 'node-form2');
+    const mid1 = w1.marker.match(/id="([^"]+)"/)![1];
+    const mid2 = w2.marker.match(/id="([^"]+)"/)![1];
+    expect(mid1).not.toBe(mid2);
+  });
+
+  test('no nodeId (legacy call): still deterministic across repeated calls, not random', () => {
+    const w1 = relayFormWiring('a@b.com', '/thx', undefined);
+    const w2 = relayFormWiring('a@b.com', '/thx', undefined);
+    expect(w1.marker).toBe(w2.marker);
+    expect(w1.actionAttr).toBe(w2.actionAttr);
+  });
+});

craft/src/utils/form-relay-wiring.ts

@@ -9,7 +9,7 @@
  * HTML — see PR #47 review).
  */
 
-import { escapeAttr, safeUrl } from './escape';
+import { escapeAttr, safeUrl, scopeId } from './escape';
 
 export interface RelayWiring {
   /** true when a recipient is set (relay path); false = legacy formAction fallback */
@@ -26,16 +26,21 @@ export interface RelayWiring {
  * @param recipientEmail the "Send submissions to" address (empty/undefined = no relay)
  * @param thankYouUrl    optional post-submit redirect (blank = hosted thank-you page)
  * @param fallbackAction the form's existing action to use when no recipient is set
+ * @param nodeId         the Craft node id of the calling form component, used to scope
+ *                        the marker/placeholder id deterministically and uniquely --
+ *                        see `scopeId` in ./escape. Falls back to a stable hash of the
+ *                        recipient/thankYouUrl/fallbackAction when omitted (never random).
  */
 export function relayFormWiring(
   recipientEmail: string | undefined,
   thankYouUrl: string | undefined,
   fallbackAction: string | undefined,
+  nodeId?: string,
 ): RelayWiring {
   if (!recipientEmail) {
     return { useRelay: false, marker: '', actionAttr: escapeAttr(safeUrl(fallbackAction || '#')), honeypot: '' };
   }
-  const fid = 'F' + Math.random().toString(36).slice(2, 8);
+  const fid = scopeId(nodeId, `${recipientEmail}::${thankYouUrl || ''}::${fallbackAction || ''}`, 'F');
   return {
     useRelay: true,
     marker: `<!--WHP-FORM id="${fid}" recipient="${escapeAttr(recipientEmail)}" thankyou="${escapeAttr(thankYouUrl || '')}"-->`,