show suggested link targets in agent prompts

Agents were flying blind — they could see nodes to review and the
topology header, but had no way to discover what targets to link to.
Now each node shows its top 8 text-similar semantic nodes that aren't
already neighbors, giving agents a search-like capability.

Also added section-level targeting guidance to linker.md, transfer.md,
and replay.md prompts: always target the most specific section, not
the file-level node.

Co-Authored-By: ProofOfConcept <poc@bcachefs.org>

prompts/transfer.md

@@ -128,6 +128,13 @@ Meta-observations about patterns in the consolidation process itself.
   symmetric lock ordering when the hot path is asymmetric" is conceptual.
   Extract the conceptual version.
 
+- **Target sections, not files.** When linking to a topic file, always
+  target the most specific section: use `reflections.md#emotional-patterns`
+  not `reflections.md`. The suggested link targets show available sections.
+
+- **Use the suggested targets.** Each episode shows text-similar semantic
+  nodes not yet linked. Start from these when proposing LINK actions.
+
 {{TOPOLOGY}}
 
 ## Episodes to process