Split clearance: node-size for face detections, spacing-scaled for routing

Target-join and boundary-slot detection now use ResolveNodeSizeClearance
(node dimensions only), while under-node/proximity use
ResolveMinLineClearance (scales with NodeSpacing via ElkLayoutClearance).

Face slot gaps depend on node face geometry, not inter-node spacing.
Routing corridors should scale with spacing for visual breathing room.

Created sprint 008 for wider spacing robustness. NodeSpacing=50 still
fails on target-join (scoring/test detection mismatch needs investigation).

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

docs/implplan/SPRINT_20260401_008_ElkSharp_wider_spacing_robustness.md

@@ -0,0 +1,48 @@
+# Sprint 20260401-008 - ElkSharp Wider Spacing Robustness
+
+## Topic & Scope
+- Make the ElkSharp document-processing artifact test pass at NodeSpacing=50 (and ideally 60) without per-spacing tuning.
+- The routing pipeline currently passes all 44+ assertions only at NodeSpacing=40. Wider spacing creates different node arrangements with different edge convergence patterns (target-joins, shared lanes) that the pipeline doesn't fix.
+- Working directory: `src/__Libraries/StellaOps.ElkSharp/`.
+- Expected evidence: artifact test passing at NodeSpacing=50, regenerated PNG with visually clean routing.
+
+## Dependencies & Concurrency
+- Depends on the ElkLayoutClearance infrastructure (already in place).
+- Safe cross-module edits limited to:
+  - `src/Workflow/__Tests/StellaOps.Workflow.Renderer.Tests/`
+  - `docs/workflow/`
+
+## Documentation Prerequisites
+- `docs/code-of-conduct/CODE_OF_CONDUCT.md`
+- `src/__Libraries/StellaOps.ElkSharp/AGENTS.md`
+
+## Delivery Tracker
+
+### TASK-001 - Make artifact test pass at NodeSpacing=50
+Status: TODO
+Dependency: none
+Owners: Implementer
+Task description:
+- Set NodeSpacing=50 in the artifact test and fix all violations that arise from the wider layout.
+- Known violations at NodeSpacing=50: target-join edge/7+edge/12, shared-lane edge/7+edge/14, under-node edge/9, long-diagonal edge/11.
+- The fixes should be generic (improve the pipeline for all spacings) not spacing-specific hacks.
+
+Completion criteria:
+- [ ] Artifact test passes at NodeSpacing=50
+- [ ] Artifact test also passes at NodeSpacing=40 (no regression)
+- [ ] HybridDeterministicMode 3/3 and StraightExit 2/2 still pass
+- [ ] Regenerated PNG is visually reviewed
+
+## Execution Log
+| Date (UTC) | Update | Owner |
+| --- | --- | --- |
+| 2026-04-01 | Sprint created. NodeSpacing=50 violations identified: target-join edge/7+edge/12@body/5/left, shared-lane edge/7+edge/14, under-node edge/9, long-diagonal edge/11. ElkLayoutClearance infrastructure in place (clearance scales with spacing). | Implementer |
+| 2026-04-01 | Split clearance into node-size-based (for face detections: target-join, boundary-slot) and spacing-scaled (for routing detections: under-node, proximity). Added `ResolveNodeSizeClearance` to scoring. Identified deeper issue: scoring's `CountTargetApproachJoinViolations` doesn't detect edge/7+edge/12 at NodeSpacing=50 but the test helper does. Likely side-resolution or detection mismatch between the two implementations. Needs investigation of `ResolveTargetApproachJoinSide` differences. | Implementer |
+
+## Decisions & Risks
+- The routing optimizer finds different paths at different spacings. Fixes must be generic (improve pipeline robustness) not per-spacing patches.
+- The ElkLayoutClearance holder ensures consistent clearance across scoring/post-processing/routing.
+- Speed regression risk: wider spacing may need more iterations.
+
+## Next Checkpoints
+- Fix violations one at a time, verifying both NodeSpacing=40 and 50 after each.

src/__Libraries/StellaOps.ElkSharp/ElkEdgeRoutingScoring.BoundarySlots.cs

@@ -17,7 +17,9 @@ internal static partial class ElkEdgeRoutingScoring
     {
         var edgesById = edges.ToDictionary(edge => edge.Id, StringComparer.Ordinal);
         var nodesById = nodes.ToDictionary(node => node.Id, StringComparer.Ordinal);
-        var minClearance = ResolveMinLineClearance(nodes);
+        // Use node-size clearance for boundary-slot gaps: slot spacing depends
+        // on node face geometry, not inter-node spacing.
+        var minClearance = ResolveNodeSizeClearance(nodes);
         var coordinateTolerance = Math.Max(1d, Math.Min(6d, minClearance * 0.2d));
         var entries = new List<(string EdgeId, ElkPositionedNode Node, string Side, double Coordinate, bool IsOutgoing)>();
 

src/__Libraries/StellaOps.ElkSharp/ElkEdgeRoutingScoring.TargetJoin.cs

@@ -15,7 +15,9 @@ internal static partial class ElkEdgeRoutingScoring
         Dictionary<string, int>? severityByEdgeId,
         int severityWeight = 1)
     {
-        var minClearance = ResolveMinLineClearance(nodes);
+        // Use node-size clearance for target-join gaps: face slot spacing
+        // depends on node face geometry, not inter-node spacing.
+        var minClearance = ResolveNodeSizeClearance(nodes);
         var nodesById = nodes.ToDictionary(node => node.Id, StringComparer.Ordinal);
         var count = 0;
 

src/__Libraries/StellaOps.ElkSharp/ElkEdgeRoutingScoring.cs

@@ -239,6 +239,16 @@ internal static partial class ElkEdgeRoutingScoring
             return overrideClearance;
         }
 
+        return ResolveNodeSizeClearance(nodes);
+    }
+
+    /// <summary>
+    /// Node-size-based clearance (independent of NodeSpacing). Used for
+    /// face-related detections (target-join, boundary-slot) where the gap
+    /// depends on node face geometry, not inter-node routing corridors.
+    /// </summary>
+    private static double ResolveNodeSizeClearance(IReadOnlyCollection<ElkPositionedNode> nodes)
+    {
         var serviceNodes = nodes.Where(n => n.Kind is not "Start" and not "End").ToArray();
         return serviceNodes.Length > 0
             ? Math.Min(serviceNodes.Average(n => n.Width), serviceNodes.Average(n => n.Height)) / 2d