The client moved to the binary cell-pack and canvas overlay last
commit, so the per-tile SVG endpoint, the TileRenderer module, and the
JSON shape of /weather/cells are all dead code. Remove them.
/weather/cells now always returns the binary WCEL pack (the ?format=bin
toggle is gone — there's only one format). The data-weather-tile-url
attribute and the weather_tile_url assign are dropped from the LiveView.
Also fix a latent bug surfaced once tests covered the default-layers
path: nil row values were writing the atom :nan into the binary segment
at runtime. Replaced with the explicit f32 quiet-NaN bit pattern so
Number.isNaN flags them correctly on the JS side.
Graham McIntire
2de1b89efc