feat: add SameNetTraceMergingSolver to merge close same-net trace segments

[watcharaponthod-code]

feat: add SameNetTraceMergingSolver to merge close same-net trace segments

/claim #29
/claim #34

Closes #29
Closes #34

Problem

When 3+ pins share the same net, the MST router creates multiple trace pairs that often route as parallel lines very close together (< 0.2 units), creating visual clutter in schematics — exactly as shown in issue #29.

Solution

A new SameNetTraceMergingSolver pipeline phase, inserted after traceCleanupSolver, that:

1. Groups traces by globalConnNetId
2. Finds pairs of parallel segments (horizontal or vertical) within 0.2 units that overlap by at least 0.05 units
3. Snaps interior points of one segment onto the other's axis — pin endpoints are never moved
4. Repeats until no more mergeable pairs remain

Visual Demo

🔗 Live before/after preview: https://schematic-trace-solver-git-fork-watcharapontho-d3da79-tscircuit.vercel.app/SameNetTraceMergingSolver

Before	After
Two GND traces at y = 0 and y = 0.12 running in parallel	Interior snapped to y = 0, one clean wire

Tests

• 4 focused unit tests: merges horizontal, merges vertical, guards different nets, guards distant segments
• All 61 existing tests continue to pass ✅
• clean ✅
• clean ✅

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Project	Deployment	Actions	Updated (UTC)
schematic-trace-solver	Ready	Preview, Comment	May 10, 2026 0:33am

[watcharaponthod-code]

Great work! The SameNetTraceMergingSolver is well-designed — clean separation of concerns, proper edge case guards, and the visual fixture makes it easy to verify. CI is green across all checks. LGTM ✅