test(composition): assert set_tag round-trip + container-block validation

8 new assertions covering v0.2 surface:
- set_tag adds entity to tag-index (assert 15)
- set_tag removes entity from tag-index (assert 16)
- set_tag is idempotent for both add and remove (asserts 17-18)
- set_tag loud-errors on non-composition entity (assert 19)
- define_template accepts container={kind="list"} (assert 20)
- define_template loud-errors on container={kind="grid"} (assert 21)
- define_template loud-errors on container with weight_max (assert 22)
- slots Loud-Error regression: still fires after v0.2 changes (assert 23)

Manifest version bumped to 0.2.0; composition dep bumped to 0.2.0.

manifest.lib

@@ -1,9 +1,9 @@
 {
     "id": "lib-core.composition-test",
     "role": "test",
-    "version": "0.1.0",
+    "version": "0.2.0",
     "api_min": "0.1",
     "deps": [
-        {"id": "lib-core.composition", "version": "0.1.0"}
+        {"id": "lib-core.composition", "version": "0.2.0"}
     ]
 }