Optimize finalized surface artwork

docs/DEVELOPMENT.md

@@ -284,6 +284,35 @@ godot --headless --path . --script scripts/normalize_texture_imports.gd \
 godot --headless --path . --script tests/texture_sampling_validation.gd
 ```
 
+### Surface artwork runtime
+
+Art Kit cells are authoritative palette and author planes, not per-cell nodes
+or dictionaries. Keep `SurfaceDrawingCellBuffer` as the live representation;
+materialize the legacy cell-array view only for inspection and tests. Finished
+artwork uses a full-resolution nearest-neighbor texture on a coarse,
+surface-conforming mesh. It discards guide and brush transforms, receives a
+distance visibility range, and unloads its render node when far from the local
+player while retaining compact session state.
+
+`surface_drawing_v3` snapshots carry packed palette and participant-index
+planes. The host sends late-join snapshots over multiple frames, prioritizing
+active and nearby canvases, so adding finished work must not restore a
+single-frame snapshot burst. Active editing and finalized artwork have
+separate bounded budgets; finalizing a canvas frees active-grid capacity.
+
+The finalized budget holds 512 maximum-size (128 x 128) canvases. At the
+current 0.075-meter cell size, 441 canvases can tile the full 200 x 200-meter
+generated-world footprint. If the generated world grows, update the finalized
+canvas and cell budgets together and rerun the artwork performance validation.
+
+Run both focused validations after changing this path:
+
+```sh
+godot --headless --path . --script tests/surface_drawing_validation.gd
+godot --headless --path . \
+  --script tests/surface_drawing_performance_validation.gd
+```
+
 ### Importing animalese voice sets
 
 Animalese clips use one deterministic runtime level and format: -18 dBFS RMS