Fix SingleLayerNodeMerger adjacency/vertical merge logic and tame obstacle filtering for single-layer nodes

[ShiboSoftwareDev]

Summary

• Resolves a merge bug in SingleLayerNodeMerger that created a spurious blocking node (e.g., cn2450) and could block the node above it.
• Reduces false-positive filtering of single-layer tiles under obstacles to avoid unnecessary blockers (e.g., cn2293-like
cases).
• Removes temporary debug logging added during investigation.

Root cause

• SingleLayerNodeMerger:
• The root node could appear in its own adjacency list, and absorbed nodes could leak back via _adjacentNodeIds updates.
• Vertical merge direction logic was inverted for TOP/BOTTOM, causing growth into the wrong direction.
• Targets from different connections could be merged together, incorrectly creating larger blocking regions.
• CapacityMeshNodeSolver2 (nodes under obstacles):
• Single-layer nodes were filtered whenever any obstacle overlap was detected, even for small overlaps, creating unnecessary blockers around pads.

/claim #285
/fixes #285

[vercel]

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[seveibar]

good attempt!

https://share.cleanshot.com/JVCC4qpD

[seveibar]

FWIW i think for autorouter PRs if your snapshot doesn't show it it's a really good idea to explain with screenshots. It's also a really good idea to make a snapshot diff prior to the PR for a particular phase so that we can see the difference, these PRs take longer to review because i have to go through that process manually with the debugger

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Project	Deployment	Preview	Comments	Updated (UTC)
capacity-node-autorouter	Ready	Preview	Comment	Oct 12, 2025 4:33pm

[seveibar]

Ok just checked it out, i THINK this looks ok, I would like to add a snapshot using stackGraphicsHorizontally that shows the before/after of the node merging phase

To make this, you can load e2e 3 and solveToStage("whateverispriortonodemerge"), record the visualize(), then solveToStage("nodemerge") and you should be able to do stackGraphicsHorizontally([stageBefore, stageAfter]), ideally we could snapshot this prior to this PR

anyway great work, checking out the code now

[seveibar]

👍 code is good. Let's add the snapshot- lmk if you want a hand doing it and i can add to my queue