fix: add lib-core.panel to test manifest deps

The test init.lua requires lib-core.panel directly; the engine resolver
enforces explicit dependency declaration and does not traverse transitive
deps from inventory-list-display.

manifest.lib

@@ -5,7 +5,8 @@
     "api_min": "0.1",
     "deps": [
         {"id": "lib-core.inventory-list-display", "version": "0.1.0"},
+        {"id": "lib-core.panel", "version": "0.1.0"},
         {"id": "lib-core.inventory-list", "version": "0.1.0"},
         {"id": "lib-core.composition", "version": "0.2.0"}
     ]
-}
+}