Tiles, Tilemaps: older projects are no longer converted on load (#137)

Tilemaps.md

@@ -180,8 +180,7 @@ is an empty cell, and a single cell drops the count:
 
 Cells outside the grid are stored as well, so a map that was made smaller gets them back when it
 grows again. Measured: a full map of 100 × 100 cells on two layers went from 736 KB to 11 KB.
-**Older projects** still load — their cells are read as they are and written in the new form on
-the next save.
+The map of the first version (#128) is not read any more (#137): such a layer loads empty.
 
 ## What it does not do yet
 

Tiles.md

@@ -2,7 +2,8 @@
 
 A **tile** is what a [tilemap](Tilemaps) paints with. It is its own asset, not part of a map: the
 same grass is used by several maps, the same way a texture is worn by several sprites. Until #131
-the asset was called *autotile*; projects saved before that open unchanged (see below).
+the asset was called *autotile*; a project still holding that type loses those assets on load
+(no migration, #137).
 
 A tile is one of three **kinds**:
 
@@ -87,9 +88,3 @@ Kind, rate, playback, the solid switch and the collision scale are ordinary prop
 A tile is never placed by itself: it is laid down by a [tilemap](Tilemaps), which is the asset
 that carries a grid of cells and is placed in a scene. Two different tiles do not join each other
 there — each autotile closes against everything else, as the RPG-Maker sheets are drawn.
-
-## Older projects
-
-A project saved before #131 holds `autotile` assets. Loading it turns them into `tile` assets
-without a word, and one that had no kind stored becomes a **Floor** — what it meant then — rather
-than falling to the new default *None*. Nothing else changes; saving writes the new name.