test(wpmc S4): restore ACF-missing guard assertions + tighten stub signature

Re-add ->never() to both noop tests so Brain Monkey/Mockery actively asserts
acf_add_local_field_group is never called when ACF is absent.  Order matters:
expect() must precede when('function_exists')->alias() so FunctionStub sees the
real function_exists and skips the eval() path (function already declared in
acf-stubs.php).  Also tighten stub signature to match real ACF ($field_group,
no type hint, no default).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/TermMetaTest.php

@@ -19,15 +19,18 @@ final class TermMetaTest extends TestCase
 
     public function test_do_register_is_noop_when_acf_missing(): void
     {
+        // Set up the ->never() expectation BEFORE aliasing function_exists, so that
+        // FunctionStub::__construct() sees the real function_exists and skips the
+        // eval() path (the function is already declared in acf-stubs.php).
+        \Brain\Monkey\Functions\expect('acf_add_local_field_group')->never();
         \Brain\Monkey\Functions\when('function_exists')->alias(function ($name) {
             return $name !== 'acf_add_local_field_group';
         });
 
-        // acf_add_local_field_group is NOT stubbed here: if do_register() called it,
-        // the Brain\Monkey eval-stub would throw MissingFunctionExpectations.
-        // We just verify the method returns without error.
         TermMeta::do_register();
 
+        // ->never() above is the actual guard assertion; assertTrue keeps
+        // PHPUnit happy under failOnRisky.
         self::assertTrue(true);
     }