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.

README.md

@@ -0,0 +1,11 @@
+# sporel-module-map-editor-test
+
+Headless asserts for the editor's API chain: load a fresh map, paint and erase cells, set roof flags, save to disk, re-load, verify state round-trips.
+
+Launches as a `kind=test-module` — all asserts run in `init()` and the module exits.
+
+```bash
+$SPOREL_BIN --module sporel-module-map-editor-test
+```
+
+Or via the engine's `test-all-modules.sh` aggregator (auto-discovers `kind:test-module`).