Add tests for maybe isSuperTypeOf path in ConditionalType::isResolvable()

Mutation testing showed the `$isSuperType->no()` branch was not
specifically covered. Added:

- NSRT test with a multi-template conditional return type where
  premature resolution (incorrectly treating `maybe` as resolvable)
  would collapse `non-empty-list` to `list`
- Rule test data for `maybe` cases (T of string|int with target string)
  verifying no false "unresolvable type" errors are reported

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

Author: phpstan-bot

tests/PHPStan/Analyser/nsrt/bug-11894.php

@@ -51,3 +51,20 @@ function testNotFullyNarrowable(mixed $a): void
 {
 	assertType('string|T of int (function Bug11894Nsrt\testNotFullyNarrowable(), argument)', conditionalReturn($a));
 }
+
+abstract class ConditionalArrayKeys
+{
+	/**
+	 * @template TKey of array-key
+	 * @template TArray of array<TKey, mixed>
+	 * @param TArray $array
+	 * @return (TArray is non-empty-array ? non-empty-list<TKey> : list<TKey>)
+	 */
+	abstract public function arrayKeys(array $array): array;
+
+	/** @param non-empty-array<int, int> $nonEmpty */
+	public function testMaybeStaysUnresolved(array $nonEmpty): void
+	{
+		assertType('non-empty-list<int>', $this->arrayKeys($nonEmpty));
+	}
+}

tests/PHPStan/Rules/Functions/data/bug-11894.php

@@ -68,3 +68,12 @@ function testNoRelation(mixed $a): mixed
 
 	return conditionalReturn($a);
 }
+
+/**
+ * @template T of string|int
+ * @param T $a
+ */
+function testMaybeRelation(mixed $a): mixed
+{
+	return conditionalReturn($a);
+}

tests/PHPStan/Rules/Methods/data/bug-11894.php

@@ -59,4 +59,23 @@ public function testStaticMethod(mixed $a): mixed
 
 		return Converter::conditionalReturnStatic($a);
 	}
+
+	/**
+	 * @template T of string|int
+	 * @param T $a
+	 */
+	public function testMaybeMethod(mixed $a): mixed
+	{
+		$c = new Converter();
+		return $c->conditionalReturn($a);
+	}
+
+	/**
+	 * @template T of string|int
+	 * @param T $a
+	 */
+	public function testMaybeStaticMethod(mixed $a): mixed
+	{
+		return Converter::conditionalReturnStatic($a);
+	}
 }