feat: add Jarvis agent verification foundation

Add Day 1 agent runtime foundations with task and event schemas, verifier support, capability metadata, graph event tracing, and regression coverage while preserving the direct execution path.

backend/app/agents/registry/__init__.py

@@ -1,11 +1,19 @@
 """Registry manifest models and validation helpers."""
 
+from functools import lru_cache
+
 from app.agents.registry.indexes import RegistryIndexes, build_registry_indexes
 from app.agents.registry.loader import RegistryBundle, load_builtin_registry_bundle
 
+@lru_cache(maxsize=1)
+def load_builtin_registry_indexes() -> RegistryIndexes:
+    return build_registry_indexes(load_builtin_registry_bundle())
+
+
 __all__ = [
     "RegistryBundle",
     "RegistryIndexes",
     "build_registry_indexes",
     "load_builtin_registry_bundle",
+    "load_builtin_registry_indexes",
 ]