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>

README.md

@@ -7,6 +7,7 @@ Dig out your underground realm, claim the portal to attract creatures, keep them
 - 3D isometric view with a freely rotatable and tiltable camera
 - Procedural pixel art, irregular cave walls, flickering torch light
 - CP437 text-mode style interface with the DINOBYTE bitmap font
+- Map sizes from 64×64 to 256×256 tiles (one portal per 64×64 tiles, guarded treasure caves on bigger maps)
 - English and German (language files in `lang/`, easy to extend)
 
 See [DESIGN.md](DESIGN.md) for all design decisions and [CREDITS.md](CREDITS.md) for third-party assets.