Add Network, BYOM, and Native Assistant operator events

[mdheller]

Summary

Adds AgentTerm operator-event coverage for the SourceOS Network Door, BYOM / external model-provider route, and Native Assistant Door evidence lanes.

This is intentionally event-only. AgentTerm records operator intent and policy posture; it does not mutate firewall state, install mesh components, contact BYOM providers, store credentials, invoke native assistant APIs, send prompts, or bypass Policy Fabric.

Changes

• Adds docs/integration/network-native-assistant-events.md.
• Adds tests proving AgentTerm can record:
  • network_door_plan
  • external_model_provider_route
  • native_assistant_bridge
• Aligns those events to AgentPlane evidence kinds:
  • NetworkDoorPlanEvidence
  • ExternalModelProviderRouteEvidence
  • NativeAssistantBridgeEvidence
• Documents future interactive shell slash aliases:
  • /network plan <destination>
  • /byom provider <profile-ref>
  • /native-assistant plan <operation>

Boundary

AgentTerm remains the Matrix-first operator surface and local event log. Execution delegates to:

sourceosctl network ...
sourceosctl native-assistant ...
AgentPlane evidence imports
Policy Fabric approvals

Validation

Expected repo validation:

pytest