Extract app runtime shell, canvas render shell, and node tree services

src/legacy_canvas_render_shell_services.h

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+#pragma once
+
+#include "canvas.h"
+
+class Canvas;
+
+namespace pp::panopainter {
+
+void legacy_canvas_draw_merge_temporary_paint_branch(
+    Canvas& canvas,
+    int layer_index,
+    int plane_index,
+    std::shared_ptr<Layer> layer,
+    const Brush& brush,
+    const glm::mat4& ortho);
+void legacy_canvas_draw_merge_branch_orchestration(
+    Canvas& canvas,
+    int plane_index,
+    int layer_index,
+    const std::shared_ptr<Layer>& layer,
+    const Brush& brush,
+    const glm::mat4& ortho,
+    bool use_blend,
+    bool copy_blend_destination);
+void legacy_canvas_draw_merge_final_plane_composite(
+    Canvas& canvas,
+    const glm::mat4& ortho,
+    bool draw_checkerboard);
+void legacy_canvas_stroke_commit_timelapse(Canvas& canvas);
+void legacy_canvas_draw_merge(
+    Canvas& canvas,
+    bool draw_checkerboard,
+    std::array<bool, 6> faces = SIXPLETTE(true));
+void legacy_canvas_destroy(Canvas& canvas);
+bool legacy_canvas_create(Canvas& canvas, int width, int height);
+void legacy_canvas_clear_context(Canvas& canvas);
+CameraData legacy_canvas_render_shell_get_camera(const Canvas& canvas);
+void legacy_canvas_render_shell_set_camera(Canvas& canvas, const CameraData& camera);
+
+} // namespace pp::panopainter