- fill_mode 'glow': uniform darkness over every room; lit lamps render
radial gradient pools (rgb_color -> color temp via kelvinToRgb ->
configurable default; brightness scales alpha)
- pools clipped by the source's room + doorway sectors (doorSector rays
to door edges; hasRoomBehind blocks entrance doors); windows and
islands don't participate (no shadow casting, documented)
- glow radius in HA units (m/ft) in general settings, stored in cm;
palette group glow_base/glow_light; backend schema updated
- +4 unit tests (98 total); smoke_glow.mjs (10 checks); docs same-commit
