BAT-014 Design

Architecture summary

adapters/mcp/tool_contracts.py becomes the MCP adapter’s narrow contract dependency surface.
adapters/streamlit/{overview,assets,transactions,categorization,imports,accounts,transfers,reconciliation}_gateway.py expose page/domain-sized call sets.
adapters/streamlit/service_gateway.py remains a compatibility aggregator while dashboard/app.py shifts to page/domain gateway aliases.
Baseline docs record the post-Phase-7 structure and runtime flow.