Replaces the static painted legend with real checkboxes (one per
GNSS system, color-swatched to match GNSS_COLORS) so users can
toggle which constellations show in the sky plot and satellite
table, mirroring the existing receiver-source filter checkboxes.
- Store up to 1 hour of (elevation, azimuth) history per satellite/source
- Trail column in satellite table (checkbox, default off); clicking the
column header toggles all trails on/off
- Trail rendered in GNSS color with alpha fading from 15 (oldest) to 200
(newest), subsampled to max 120 points for render performance
- Trail column fixed at 42 px to avoid checkbox + empty-text visual split
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
jens
