feat: merge nearby same-net trace segments

[nicovaleops]

Closes #29.

/claim #29

Summary

• Adds SameNetTraceSegmentMergeSolver as a dedicated pipeline phase after trace cleanup and before the second net-label placement pass.
• Merges nearby trace paths only when they share the same effective net key (userNetId, then globalConnNetId, then dcConnNetId).
• Handles reversed orientations, exact/near endpoint joins, orthogonal bridge insertion, duplicate endpoint removal, and collinear simplification.
• Preserves merged mspConnectionPairIds and pinIds without duplicates.
• Adds focused tests for same-net merge and different-net non-merge behavior.

Validation

Prepared patch validation before submission:

• npx tsc --noEmit passed
• npx biome check --write passed on the new solver/test files
• git diff --check passed

Submission-run validation:

• Patch cleanly applied to current origin/main (d81247e / v0.0.57)
• bun test could not be run in this environment because bun is not installed

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Project	Deployment	Actions	Updated (UTC)
schematic-trace-solver	Ready	Preview, Comment	May 14, 2026 2:21am

[digzrow-coder]

This does not actually combine the close parallel same-net segments that #29/#34 are about. The merge criterion only looks at endpoint-to-endpoint Manhattan distance, then concatenates both paths with a bridge. For two duplicated same-net horizontal runs that overlap and are 0.05 apart, e.g.

[{ x: 0, y: 0 }, { x: 2, y: 0 }]
[{ x: 0, y: 0.05 }, { x: 2, y: 0.05 }]

with the PR's maxEndpointGap: 0.12, the solver outputs a single path shaped like a loop/rectangle:

[
  { x: 0, y: 0 },
  { x: 2, y: 0 },
  { x: 2, y: 0.05 },
  { x: 0, y: 0.05 },
]

That preserves both parallel runs and adds a vertical connector; it does not snap/merge them onto one shared X/Y axis, so the visual duplication from the bounty remains. The tests only cover an endpoint-gap join, not the near-overlapping parallel segment case shown in the issue screenshots.

The merge phase needs segment-level overlap/alignment logic: detect same-net H/H or V/V segments with small orthogonal separation and overlapping spans, choose a shared axis, and rewrite the duplicated runs onto that axis while preserving pin endpoints and avoiding unsafe crossings.

[nicovaleops]

Thanks for the concrete review. I pushed a follow-up commit (87a787f) that handles the overlapping-parallel-segment case directly before falling back to endpoint bridging.

What changed:

• detects same-net H/H or V/V single-segment traces with overlapping spans and small orthogonal separation
• collapses them onto one shared axis instead of creating a loop/rectangle bridge
• keeps the previous endpoint-gap merge behavior for non-overlap joins
• added regression coverage for the exact parallel horizontal example from the review

Verification run locally:

• npx bun test tests/solvers/same-net-trace-segment-merge-solver/same-net-trace-segment-merge-solver.test.ts
• npm run build