Fix initializedEmpty not propagating through createFromConstantArray round-trips

When processing `$a = []; $a[-10] = 'a'; $a[-5] = 'b';`, the second
assignment creates a new builder via createFromConstantArray with a
non-empty array, losing the initializedEmpty flag. This caused
shouldUpdateAutoIndex to incorrectly return true on PHP 8.0-8.2.

Fix: in createFromConstantArray, also infer initializedEmpty when the
source array has negative int keys but max(nextAutoIndexes) === 0,
since a non-empty initializer on PHP 8.0+ would have already bumped
the auto-index.

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

Author: phpstan-bot

src/Type/Constant/ConstantArrayTypeBuilder.php

@@ -77,6 +77,13 @@ public static function createFromConstantArray(ConstantArrayType $startArrayType
 
 		if (count($startArrayType->getKeyTypes()) === 0) {
 			$builder->initializedEmpty = true;
+		} elseif (max($startArrayType->getNextAutoIndexes()) === 0) {
+			foreach ($startArrayType->getKeyTypes() as $keyType) {
+				if ($keyType instanceof ConstantIntegerType && $keyType->getValue() < 0) {
+					$builder->initializedEmpty = true;
+					break;
+				}
+			}
 		}
 
 		if (count($startArrayType->getKeyTypes()) > self::ARRAY_COUNT_LIMIT) {