test(form-builder): registry/model alignment consistency invariant (WS-6)

Sessie 1 left BindingTypeRegistryConsistencyTest as the cross-cutting
invariant for the binding registry. This commit extends it with a
new assertion: every registry entity must map to a real Eloquent
model class, and every registry attribute must exist as a column
on that model's table.

Future drift (someone adds a registry attribute without the column,
or renames a column without updating the registry) becomes a test
failure on the next test run, not a runtime surprise.

Implementation: queries information_schema.COLUMNS via the active
MySQL connection (opaque DBs are not in Crewli's deployment matrix
per CLAUDE.md). Skips the 'artist' entity entirely — it's
intentionally absent from v1 registry per BACKLOG
ARTIST-ADV-BINDING-MODEL.

Pre-existing tests not touched by this commit (already updated in
previous Task 2 commit a404865 for the renames):
  - BindingTypeRegistryTest (collection-target tests use Config::set
    synthetic injection)
  - AppendStrategyRequiresCollectionTargetTest (same pattern)
  - MaxOneIdentityKeyPerTargetEntityTest (company.email →
    company.contact_email)

Refs: WS-6 sessie 3a binding-target drift audit

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

api/tests/Feature/FormBuilder/Bindings/BindingTypeRegistryConsistencyTest.php

@@ -8,6 +8,7 @@ use App\Enums\FormBuilder\BindingTargetType;
 use App\FormBuilder\Bindings\BindingTypeRegistry;
 use App\FormBuilder\Publishing\RequiresIdentityKeyBinding;
 use App\FormBuilder\Purposes\PurposeRegistry;
+use Illuminate\Support\Facades\DB;
 use Tests\TestCase;
 
 /**
@@ -91,4 +92,69 @@ final class BindingTypeRegistryConsistencyTest extends TestCase
             }
         }
     }
+
+    /**
+     * Sessie 3a.5 — drift-prevention invariant: every registry entity
+     * must map to a real Eloquent model class, and every registry
+     * attribute must exist as a column on that model's table.
+     *
+     * Without this assertion, a renamed model column or a typo in
+     * binding_targets.php only surfaces at apply time (or worse, in
+     * production after publish). With it, drift becomes a test
+     * failure on the next test run.
+     */
+    public function test_every_registry_entity_maps_to_an_eloquent_model_with_the_attribute(): void
+    {
+        $entityToModel = [
+            'person' => \App\Models\Person::class,
+            'company' => \App\Models\Company::class,
+            'user' => \App\Models\User::class,
+            // Note: 'artist' intentionally absent from registry in v1
+            // (BACKLOG ARTIST-ADV-BINDING-MODEL).
+        ];
+
+        $registry = config('form_builder.binding_targets');
+        $this->assertIsArray($registry);
+
+        foreach ($registry as $entity => $attributes) {
+            $this->assertArrayHasKey(
+                $entity,
+                $entityToModel,
+                "Registry entity '{$entity}' has no Eloquent model class mapped. "
+                ."Add it to entityToModel here, or remove the entity from the registry.",
+            );
+
+            $modelClass = $entityToModel[$entity];
+            $this->assertTrue(
+                class_exists($modelClass),
+                "Entity '{$entity}' maps to {$modelClass} but the class does not exist.",
+            );
+
+            $instance = new $modelClass;
+            $columns = $this->columnsOnTable($instance->getTable());
+
+            foreach (array_keys($attributes) as $attribute) {
+                $this->assertContains(
+                    $attribute,
+                    $columns,
+                    "Registry says '{$entity}.{$attribute}' exists, but column "
+                    ."'{$attribute}' is not on table '{$instance->getTable()}'.",
+                );
+            }
+        }
+    }
+
+    /**
+     * @return list<string>
+     */
+    private function columnsOnTable(string $table): array
+    {
+        $rows = DB::select(
+            'SELECT COLUMN_NAME FROM information_schema.COLUMNS '
+            .'WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = ?',
+            [$table],
+        );
+
+        return array_map(static fn (object $r): string => (string) $r->COLUMN_NAME, $rows);
+    }
 }