Rendering optimization #78 (#81)

[bridgesign]

• Replace per-layer surfaces with single render surface + per-artist RGBA cache

• Reuse graph cache across camera moves via offset blit and zoom stretch

• Substitute short edges and skip sub-pixel edges and nodes in graph rendering

• Clean up docstring formatting in default_drawers

• Move cached artist rendering behind a RenderManager callback

• Merge get_culling_bounds and world_to_screen_scale into get_viewport

• Skip edge.linestring access for short or cached edges in graph rendering

• Move constants to init

• Revert graph render cache to lazy edge_line_points dict

• Apply skip/short edge optimization to render_map_sensor

• Avoid strip re-render and bilinear cost on zoom-out

• Clarify cached artist handler docstring

• render agent optimization

• get_edges in a box

• edge caching in waiting_simulation

• edge finding optimizations

• Fix projection updates on window resize

• Remove will_draw from artist interfaces and use ArtistType for static cache routing

• Replace per-artist pixel caches with per-layer surfaces

• Guard render projection against zero screen size

• Change layer cache artist_names from set to tuple

• cache mismatch bug fix

• Remove unused _static_layers from RenderManager

• Clamp render dimensions on resize

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