refactor(form-builder): strict validator on save; strip rules.unique fallback

api/app/Services/FormBuilder/FormFieldValidationRuleService.php

@@ -53,9 +53,7 @@ final class FormFieldValidationRuleService
      */
     public function replaceRules(FormField|FormFieldLibrary $owner, array $specs): void
     {
-        foreach ($specs as $spec) {
-            $this->assertSpecValid($spec);
-        }
+        $this->assertSpecsValid($specs);
 
         $ownerType = $this->ownerTypeFor($owner);
 
@@ -182,6 +180,21 @@ final class FormFieldValidationRuleService
         };
     }
 
+    /**
+     * Public wrapper around `assertSpecValid` — iterates a caller-supplied
+     * list and throws the first `UnknownValidationRuleTypeException`.
+     * Used by FormRequests (WS-5b commit 3 strict validator on save) to
+     * reject bad specs at the HTTP boundary before any write lands.
+     *
+     * @param  list<array<string, mixed>>  $specs
+     */
+    public function assertSpecsValid(array $specs): void
+    {
+        foreach ($specs as $spec) {
+            $this->assertSpecValid($spec);
+        }
+    }
+
     private function ownerTypeFor(FormField|FormFieldLibrary $owner): string
     {
         return $owner instanceof FormField ? 'form_field' : 'form_field_library';