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

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+# 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.