fix: use plain {%if%} tags in TYPE_CHECKING block to avoid collapsing import line

{%- lstrip was stripping the newline after `if TYPE_CHECKING:`,
collapsing it onto the same line as the first import. trim_blocks=True
(Copier default) makes plain {% if %} tags invisible on their own lines.

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

Author: namitdeb739