fix: only treat the last path segment as a filename in path()

isFilePath() checked the entire path for a dot to decide whether path() was given
a file or a directory. Because the path includes the location and name, a dot in
a parent segment (for example a location like /tmp/my.app) caused a directory
argument to be misclassified as a file, so the requested subdirectory was not
created. Inspect only the last path segment instead.

src/TemporaryDirectory.php

@@ -163,7 +163,12 @@ class TemporaryDirectory
 
     protected function isFilePath(string $path): bool
     {
-        return str_contains($path, '.');
+        // Only the last segment can be a filename; a dot in a parent segment would
+        // misclassify a directory.
+        $lastSeparator = strrpos($path, DIRECTORY_SEPARATOR);
+        $lastSegment = $lastSeparator === false ? $path : substr($path, $lastSeparator + 1);
+
+        return str_contains($lastSegment, '.');
     }
 
     protected function deleteDirectory(string $path): bool