feat(grid-agent): establish architecture and config (#118)

config/grid-agent.example.json

@@ -0,0 +1,29 @@
+{
+  "integrated": false,
+  "split": false,
+  "llm": {
+    "endpoint_url": "https://llm.example.invalid/v1/chat/completions",
+    "api_key": "<set-via-environment-or-restricted-secret-file>"
+  },
+  "authorized_avatar_uuids": [],
+  "timeouts": {
+    "startup_seconds": 30,
+    "shutdown_seconds": 10,
+    "request_seconds": 60
+  },
+  "limits": {
+    "grid_event_queue": 256,
+    "control_queue": 32,
+    "observable_queue": 512,
+    "max_body_bytes": 1048576,
+    "max_message_bytes": 16384,
+    "max_conversation_messages": 64,
+    "max_tool_calls": 16,
+    "max_authorized_avatars": 128,
+    "max_background_tasks": 2
+  },
+  "storage_path": "data/grid-agent",
+  "behavior": {
+    "heartbeat_seconds": 30
+  }
+}