fix(render): the one-cell tiling renderer starts outside any knockout group (#2971)

After rebasing onto main: #3356's one-cell pattern renderer (merged) builds
a Renderer without the knockout fields this PR adds. Like the tiled cell's
renderer, a pattern cell is painted as its own artwork, so it starts with
no knockout group open.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv2WwdgjmBz33GWkwgNn3Q

vendor/hayro/src/renderer.rs

@@ -1188,6 +1188,9 @@ impl Renderer {
                                 ),
                                 color_replacement: None,
                                 in_annotations: false,
+                                knockout: Vec::new(),
+                                erasing: false,
+                                erase_groups: 0,
                                 cur_mask: None,
                                 inside_pattern: true,
                                 soft_mask_cache: HashMap::default(),