feat: Fibonacci spiral canvas + graph filter + domain sub-hubs

- Wiki Map.canvas: 13 nodes at golden angle 137.5deg (Fibonacci/sunflower pattern)
  - index at center, 3 domain _indexes in ring 1, content in outer rings
  - Color coded: orange=concepts, purple=entities, green=sources, blue=navigation
  - 17 semantic edges with labels
- graph.json: search:path:wiki — eliminates all plugin file noise
  - hideUnresolved:true — removes phantom Subject A/B nodes
  - nodeSizeMultiplier 1.8 — hub nodes visually dominant
  - repelStrength 30 — clean radial spreading
- Created wiki/concepts/_index.md, wiki/entities/_index.md, wiki/sources/_index.md
  - These are domain hub nodes that create the 3-ring hierarchy in graph view
- All wiki pages now link to their domain _index
  - Creates proper hub-and-spoke topology in force-directed graph

wiki/sources/Nate Herk LLM Wiki Transcript.md

@@ -27,6 +27,7 @@ related:
   - "[[Compounding Knowledge]]"
   - "[[Andrej Karpathy]]"
   - "[[index]]"
+  - "[[sources/_index]]"
 sources:
   - "[[.raw/nate-herk-llm-wiki-transcript.md]]"
 ---