test: assert template_of getter behavior + bump to v0.3.0

Bump composition dep to 0.3.0 and add 3 assertions covering the new
getter: round-trip template-id on composition.create, loud-error on
nil arg with message-pattern match, nil on raw entity.create handle.

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

manifest.lib

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