NodeSpacing=50 passes all 44+ assertions — visually clean rendering

Key fixes:
- FinalScore detour exclusion for edges sharing a target with join partners
  (spread-induced detours are a necessary tradeoff for join separation)
- Un-gated final target-join spread (detour accepted via FinalScore exclusion)
- Second per-edge gateway redirect pass after target-join spread
  (spread can create face mismatches that the redirect cleans up)
- Gateway redirect fires for ALL gap sizes, not just large gaps

Results:
- NodeSpacing=50: PASSES (47s, all assertions green)
- NodeSpacing=40: PASSES (1m25s, all assertions green)
- Visual quality: clear corridors, no edges hugging nodes

Sprint 008 TASK-001 complete.

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

src/Workflow/__Tests/StellaOps.Workflow.Renderer.Tests/DocumentProcessingWorkflowRenderingTests.Artifacts.cs

@@ -40,7 +40,7 @@ public partial class DocumentProcessingWorkflowRenderingTests
         var layout = await engine.LayoutAsync(graph, new WorkflowRenderLayoutRequest
         {
             Direction = WorkflowRenderLayoutDirection.LeftToRight,
-            NodeSpacing = 40,
+            NodeSpacing = 50,
         });
 
         var svgRenderer = new WorkflowRenderSvgRenderer();