Four-stage keyer in flood_key_magenta: unchanged border flood, strict
interior-pocket key, is_magenta fringe erosion, and despill; hd_assets
inherits it via import. New --reprocess mode re-keys assets/raw sources
without API calls (skips tiles, rebuilds sheets, never touches the
manifest). Pure-key #FF00FF pockets are gone from every HD webp.
218 stills + 24 sheets generated by tools/hd_assets.py at quality 90,
~220MB total. Loaded only when HD Remaster is enabled; standard PNGs
remain the default and the per-sprite fallback.
Quintine
