Fix false fan-out: count unique consumers, not edge count

gem_to_bar had 2 edges to alloy_furnace (one enhancement, one main
from dedup) which triggered false fan-out detection, preventing
supply propagation. Alloy showed qty=8 (demand) instead of qty=6
(supply-constrained: 12 bars / 2 per alloy = 6).

Fix: count unique consumer NODE IDs, not raw edge count.
gem_to_bar → alloy (2 edges, 1 consumer) = NOT fan-out → propagate.
alloy → bolt/plate/frame/super/coiler (5 consumers) = fan-out → stop.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bod09

js/graph-builder.js

@@ -483,7 +483,8 @@ class FlowGraphBuilder {
         if (!curNode) continue;
         // Find non-byproduct edges FROM this node
         const outEdges = edges.filter(e => e.from === curId && e.kind !== "byproduct");
-        const isFanOut = outEdges.length > 1;
+        const uniqueConsumers = new Set(outEdges.map(e => e.to)).size;
+        const isFanOut = uniqueConsumers > 1;
 
         for (const edge of outEdges) {
           if (supplyVisited.has(edge.to)) continue;