Preserve tileset path and parallax style on save instead of
hardcoding tileset.png. Add tileset cycling (T key), tile flag
editing (F key for solid/platform/hazard/none), and 8x8 pixel
mini-icons for all entity types in the palette and canvas.
Fix entity palette not appearing when editor starts without a
prior level load by splitting entity_registry_init into populate
and init phases. Fix bitmap font rendering dropping the top row
by correcting FONT_H from 6 to 7. Widen toolbar button spacing.
Fix invisible collision from placed tiles lacking TileDefs by
calling ensure_tile_def on pencil and fill placement. Fix editor
hotkeys not working in the web build by latching key presses from
SDL_KEYDOWN events instead of comparing keyboard state snapshots.
372ea3d586