Remove all real map files, keep only generated map approach

Deleted:
- test-engine/maps/TestMinimal2x2.sdz (real map with SMF file)
- test-engine/maps/minimal_test_map.sdd/ directory (contained SMF file)
- games/mapinfo.lua (referenced real SMF file)
- script.txt (referenced TestMinimal map)

Changed:
- test_fixtures/minimal_test_map.sdd/mapinfo.lua: Renamed from TestMinimal2x2 to minimal_test_map, kept empty mapfile for generation

Only remaining map:
- test-engine/maps/sb_initial_blank_10x8.sdz (mapinfo.lua only, no SMF file)

All maps now use mapfile="" for terrain generation, no real SMF files exist.

Author: claude

test_fixtures/minimal_test_map.sdd/mapinfo.lua

@@ -1,8 +1,8 @@
 -- Auto-generated minimal test map
 local mapinfo = {
-  name        = "TestMinimal2x2",
-  shortname   = "test_minimal_2x2",
-  description = "Minimal 2x2 test map for CI smoke tests",
+  name        = "minimal_test_map",
+  shortname   = "minimal_test",
+  description = "Minimal test map with generated terrain",
   author      = "Auto-generated",
   version     = "v1.0",
   mapfile     = "",