fix(P.3.1): split_namespaced_id replaced with current-module-prefix match; v0.1.1

Pre-existing bug: split_namespaced_id used first-dot-split. For modules
with dotted IDs (e.g. lib-core.maps-test), this misclassified
'<dotted-module-id>.<tilemap-name>' as cross-lib reference.

Replaced with split_local_tilemap() that matches by exact current-
module-id prefix. Module-id can now have arbitrary dots.

Surfaced by P.3.1 reference test-module 'lib-core.maps-test' which
has a dotted module-id.

init.lua

@@ -16,12 +16,17 @@ local current_map_id    = nil
 -- Internal helpers
 -- =====================================================================
 
--- Splits "lib-x.foo" -> "lib-x", "foo" (split at FIRST dot only).
--- Returns (nil, full_id) if no dot present.
-local function split_namespaced_id(full_id)
-    local dot = string.find(full_id, ".", 1, true)
-    if not dot then return nil, full_id end
-    return string.sub(full_id, 1, dot-1), string.sub(full_id, dot+1)
+-- Checks whether `full_id` is a tilemap belonging to the current module.
+-- Module-IDs can themselves contain dots (e.g. `lib-core.maps-test`), so a
+-- naive first-dot-split is wrong. Match by prefix `<current-module-id>.`.
+-- Returns (is_local, local_name) — local_name is nil if not local.
+local function split_local_tilemap(full_id)
+    local mod = engine.module.id()
+    local prefix = mod .. "."
+    if string.sub(full_id, 1, #prefix) == prefix then
+        return true, string.sub(full_id, #prefix + 1)
+    end
+    return false, nil
 end
 
 -- "demo_tilemap"           -> "<current-module-id>.demo_tilemap"
@@ -82,12 +87,11 @@ local function load_tilemap(full_id)
     if tilemap_registry[full_id] then
         return tilemap_registry[full_id]
     end
-    local lib_id, local_name = split_namespaced_id(full_id)
-    local current_lib = engine.module.id()
-    if lib_id ~= current_lib then
+    local is_local, local_name = split_local_tilemap(full_id)
+    if not is_local then
         -- DEPRECATED-MVP: cross-lib tilemap resolution deferred to render-slice
         error(string.format("maps.load: cross-lib tilemap resolution deferred [DEPRECATED-MVP]; tilemap '%s' not from current module '%s'",
-            full_id, current_lib))
+            full_id, engine.module.id()))
     end
     local path = "assets/tiles/" .. local_name .. ".tilemap.json"
     local raw = engine.asset.load_json(path)