Add graph_topology, graph_health, interference_pairs tools

Convert {{topology}}, {{health}}, {{pairs}} placeholders to
{{tool:}} calls. Made format_topology_header, format_health_section,
format_pairs_section pub so tools can call them.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/subconscious/agents/extractor.agent

@@ -44,7 +44,7 @@ pattern you've found.
 - **Preserve diversity.** Multiple perspectives on the same concept are
   valuable. Only delete actual duplicates.
 
-{{TOPOLOGY}}
+{{tool: graph_topology}}
 
 ## Neighborhood nodes