bug: flow_context key missing from CrossDatabaseState — topology data silently lost between nodes

[bhavyakeerthi3]

Bug Description

identify_flow() returns {"flow_context": flow_context} andverify_mechanism() reads state.get("flow_context"), but flow_context is never declared in CrossDatabaseState.

This means the topological reasoning pipeline fetches real API data from the Reactome Content Service but never uses it — the fix is a one-line state declaration.

Minimal Reproduction

# Before fix: topology data silently lost by LangGraph
result = await builder.identify_flow(state, {})
print(result.get("flow_context"))  # Returns data ✓

# But in the next node, state never receives it:
flow_ctx = state.get("flow_context")  # None — key dropped by LangGraph ✗

Why It's Non-Obvious

LangGraph does not raise an error for undeclared state keys — it silently discards them. This makes the bug invisible in unit tests that mock state directly, since those tests never pass through the LangGraph state reducer.

Fix

Add flow_context: str to CrossDatabaseState in src/agent/profiles/cross_database.py and a regression test to prevent recurrence.

Files Affected

• src/agent/profiles/cross_database.py
• tests/test_flow_reasoning.py