Scaffold sporel-module-map-editor-test

Headless test module that exercises the lib-core.maps v0.4.0 write
APIs end-to-end: load fixture map, paint cells with rotation and
auto-allocate the wall layer, set roof flags, save to a temp file,
re-load (under a patched id to dodge registry collision), and
assert state round-trips.

manifest.core

@@ -0,0 +1,6 @@
+{
+    "id": "sporel-module-map-editor-test.core",
+    "kind": "lib",
+    "version": "0.1.0",
+    "license": "Proprietary"
+}