Migrate test assertions to atlas tile-record shape; bump to 0.3.0

tile.id is now an integer; the stable string identifier is tile.name.
Updates all tile-record string-id assertions to use .name. Adds
walkable field to stub atlas JSONs so gameplay assertions pass without
the legacy tiles dir. Test bootstrap calls maps.load_textures with
aliases pointing to the test-lib itself as the asset provider. Moves
load_textures calls inline after each set_current (Task 4 and Task 9
blocks) so all tile-record shape and walkability checks use atlas
records throughout. Bumps version to 0.3.0, dep on maps 0.3.0.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

manifest.lib

@@ -1,9 +1,9 @@
 {
     "id": "lib-core.maps-test",
     "role": "test",
-    "version": "0.2.0",
+    "version": "0.3.0",
     "api_min": "0.1",
     "deps": [
-        {"id": "lib-core.maps", "version": "0.2.0"}
+        {"id": "lib-core.maps", "version": "0.3.0"}
     ]
 }