Configurable map size (64-256, non-square), one portal per 64x64 tiles, guarded treasure caves, glowing dig-mark blocks

- New Game dialog with map width/height (steps of 32), remembered in settings
- map dimensions are per game; renderer chunks, minimap and camera follow them
- content scales with area; grace period grows with the distance to the Hero Gate
- treasure caves with rich gold, guarded by hero squads that hold their post
- marked blocks: translucent yellow box with outline on all edges
- savegame v2: packed run-length encoded tiles (256x256 map ~320 KB), v1 still loads
- tests: savegame round trip on 96x128, 256x256 generation/simulation/save

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

lang/de.lang

@@ -266,3 +266,9 @@ save.loaded = Spiel geladen.
 save.err_invalid = Diese Datei ist kein gültiger DungeonCraft-Spielstand.
 save.err_version = Dieser Spielstand stammt aus einer neueren DungeonCraft-Version.
 save.choose = Spielstand-Datei auswählen ...
+
+# ---- Neues Spiel
+newgame.width = Kartenbreite
+newgame.height = Kartenhöhe
+newgame.start = Starten
+newgame.info = {0} Portal(e), {1} bewachte Schatzhöhle(n)