init: lib-core.api-discovery-test v0.1.0 skeleton

Empty run_tests body. Assertions added incrementally via TDD in
subsequent S2-plan tasks.

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

manifest.lib

@@ -0,0 +1,9 @@
+{
+    "id": "lib-core.api-discovery-test",
+    "role": "test",
+    "version": "0.1.0",
+    "api_min": "0.1",
+    "deps": [
+        {"id": "lib-core.api-discovery", "version": "0.1.0"}
+    ]
+}