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>

init.lua

@@ -1,6 +1,7 @@
--- lib-core.composition-test — Phase A.1 + B.1
+-- lib-core.composition-test — Phase A.1 + B.1 + C.0
--- 23 assertions: 4 define_template + 4 create + 3 list_by_* + 2 destroy + 1 list_templates
+-- 26 assertions: 4 define_template + 4 create + 3 list_by_* + 2 destroy + 1 list_templates
---               + 8 B.1 (set_tag round-trip + container-block validation) + 1 slots regression.
+--               + 8 B.1 (set_tag round-trip + container-block validation) + 1 slots regression
+--               + 3 C.0 (template_of getter: round-trip, nil-arg loud-error, raw-entity nil).
 -- Pattern follows P.2.4 Test-Module-Pattern; TAP output via engine.test.*
 
 local composition = require("lib-core.composition")
@@ -194,6 +195,27 @@ function M.run_tests(ctx)
     })
     T.assert(not ok_slots_regression,
         "define_template still loud-errors on 'slots' block (Phase D regression)")
+
+    -- ================================================================
+    -- C.0 — template_of getter (3)
+    -- ================================================================
+
+    -- 1. composition.create returns entity whose template_of returns its template-id.
+    local template_of_target = composition.create{ template = "sign" }
+    T.equals(composition.template_of(template_of_target), "sign",
+        "template_of returns template-id for composition-created entity")
+
+    -- 2. template_of(nil) loud-errors with message matching "composition.template_of.*entity".
+    local ok_nil, err_nil = pcall(composition.template_of, nil)
+    T.assert(not ok_nil and type(err_nil) == "string"
+                 and string.find(err_nil, "composition%.template_of") ~= nil
+                 and string.find(err_nil, "entity")                  ~= nil,
+        "template_of(nil) loud-errors with message matching 'composition.template_of.*entity'")
+
+    -- 3. Raw engine.entity.create() entity (no composition) → template_of returns nil (no error).
+    local raw_alien = entity.create()
+    T.equals(composition.template_of(raw_alien), nil,
+        "template_of returns nil for raw entity.create() handle (not composition-managed)")
 end
 
 return M

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"}
     ]
 }