Don't route net-label-only nets as wire traces (#79)

[s300169140]

Closes #79.

Summary

Two related root causes produced spurious wire traces between pins that share only a net label:

1. Shared-state in getConnectivityMapsFromInputProblem — new ConnectivityMap(directConnMap.netMap) retained a reference to the underlying netMap, so subsequent netConnMap.addConnections(...) calls mutated directConnMap.netMap too. Pins added via netConnections appeared to be in the direct-wire connectivity. Fixed by deep-cloning before seeding.

2. MspConnectionPairSolver iterated every net, not just direct ones — queuedDcNetIds = Object.keys(netConnMap.netMap) queued every net for MSP pair creation, including net-label-only ones. The README documents the intended behavior: "Net connections will not be routed, net labels are placed instead." This change brings the code in line with that contract by queuing only direct-connection nets and reading pins from dcConnMap.

Relationship to #275

This builds on the same root-cause analysis as #275 (h/t @chengyixu) but goes further. #275 addresses the mixed case (one pin in a directConnection, another only in a netConnection) — but the pure net-label-only case (two pins sharing a net name with no direct wire between them) still produces MSP pairs and therefore visible traces.

Verified on the #275 branch:

// Two caps, GND on top pins, VCC on bottom pins, no direct wires.
directConnections: [],
netConnections: [
  { netId: "GND", pinIds: ["C1.1", "C2.1"] },
  { netId: "VCC", pinIds: ["C1.2", "C2.2"] },
],

On #275 main:

MSP pairs: 2          ← spurious
Lines solver paths: 2 ← visible traces still drawn

On this branch:

MSP pairs: 0          ← correct

This is the repro61 scenario from tscircuit/core PR #1503 — and the one I think is the actual subject of this bounty issue.

Tests

Adds tests/solvers/MspConnectionPairSolver/MspConnectionPairSolver_repro79.test.ts covering both:

• the mixed case (matches fix: prevent net-label-only nets from generating spurious traces (issue #79) #275's coverage)
• the pure net-label-only case (the additional coverage in this PR)

Updates MspConnectionPairSolver_repro1.test.ts from expect(4) to expect(2) with a comment explaining why — the previous expectation was capturing the buggy behavior (creating MST pairs for the GND netConnection).

Snapshot impact

11 example snapshots updated. I spot-checked example12 and example21 — every change is removal of spurious same-net trace lines, no unrelated drift. Happy to walk through any specific example if the diff is hard to read.

Verification

• bun test — 59 pass / 0 fail / 4 skip (was 47 pass / 12 fail before snapshot update)
• bunx tsc --noEmit — clean
• bun run format:check — clean

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Project	Deployment	Actions	Updated (UTC)
schematic-trace-solver	Ready	Preview, Comment	May 11, 2026 5:51pm