docs(craft): state the packet rollout and daemon error contracts

Clients ignore unknown packet types by design, so the artifact packet ships
before its consumer, and the sandbox daemon cannot import onyx.* so its
routes raise HTTPException rather than OnyxError. Both were review questions
twice over, the code now answers them itself.

Author: nmgarza5

backend/onyx/server/features/build/packets.py

@@ -96,6 +96,8 @@ class ArtifactPacket(BasePacket):
     Carries the full row, unlike the ids-only approval packet, so a consumer
     can render a card with no round trip. The version is pinned at announce
     time and the index refetch at turn end is the completeness guarantee.
+    No shipped client parses this type yet: clients ignore unknown packet
+    types by design, and the consumer lands with the output panel frontend.
     """
 
     type: Literal["artifact"] = "artifact"

backend/onyx/server/features/build/sandbox/image/sandbox_daemon/server.py

@@ -1,3 +1,11 @@
+"""Sandbox daemon HTTP server.
+
+Runs standalone inside the sandbox container with only stdlib, fastapi, and
+pydantic available. ``onyx.*`` is unimportable here, so routes raise
+``HTTPException`` directly instead of the api-server's ``OnyxError`` contract,
+and the api-server's SidecarClient translates failures for its callers.
+"""
+
 import asyncio
 import base64
 import binascii