draw: increase far Z, separate path for space quads, fix billboard batching

src/rendering/twn_draw_c.h

@@ -23,7 +23,7 @@ extern float camera_2d_zoom;
 
 extern double depth_range_low, depth_range_high;
 
-#define QUAD_ELEMENT_BUFFER_LENGTH (65536 / 6)
+#define QUAD_ELEMENT_BUFFER_LENGTH ((65536 * 1) / 6)
 #define CIRCLE_VERTICES_MAX 2048
 
 /* TODO: limit to only most necessary */
@@ -217,6 +217,7 @@ typedef struct ElementIndexedQuadWithoutColorWithoutTexture {
     Vec2 v3;
 } ElementIndexedQuadWithoutColorWithoutTexture;
 
+/* TODO: rename to space quad */
 /* TODO: no color variant */
 typedef struct ElementIndexedBillboard {
     /* upper-left */
@@ -334,6 +335,9 @@ void push_quad_payload_to_vertex_buffer_builder(struct QuadBatch batch,
                                                 Vec2 uv0, Vec2 uv1, Vec2 uv2, Vec2 uv3,
                                                 Color color);
 
+void finally_draw_space_quads_batch(const MeshBatch *batch,
+                                    const TextureKey texture_key);
+
 void finally_draw_text(FontData const *font_data,
                        size_t len,
                        Color color,