fix: don't route traces between net-label-only pins (#79)

[voltrace-io]

Summary

Fixes the "trace jumping" bug where the solver created routed traces between pins that share a net only via net labels (netConnections), with no directConnections between them. This is the extra net label / spurious trace issue described in #79 (see also tscircuit/core#1503).

Root causes fixed:

1. Reference mutation in getConnectivityMapsFromInputProblem — directConnMap.netMap was passed by reference into netConnMap. Subsequent addConnections() calls mutated the "direct-only" map too, so dcConnMap ended up containing net-label-only pins. Fixed by cloning the netMap.

2. Wrong map in MspConnectionPairSolver._step — Pin lookup used globalConnMap (which unions direct + net connections). Switching to dcConnMap means net-label-only nets produce zero MSP pairs and zero routed traces.

3. LongDistancePairSolver reinvented traces for label-only nets — It iterated every net in netConnMap including nets that exist only as labels. Now skips any net that has no primary MSP pair: long-distance routing should only complete partially-routed nets, never create traces for label-only nets.

Changes:

• 3 source files modified (minimal, focused diff)
• New repro61 test locks in the fix at both MSP and pipeline levels
• MspConnectionPairSolver_repro1 updated: GND (net-only, 3 pins) correctly produces 0 MSP pairs instead of 2
• 22 example snapshots regenerated — spurious net-only traces removed

Tests: 60 pass, 4 skip, 0 fail
Typecheck: bunx tsc --noEmit — no errors
Format: biome format — clean

/claim #79

Review & Testing Checklist for Human

• Verify repro61 test correctly represents the "two capacitors with only net labels" scenario from core#1503
• Spot-check 2-3 regenerated snapshots to confirm only spurious net-only traces were removed (no valid direct-connection traces lost)
• Confirm existing examples with both directConnections and netConnections still produce correct traces (e.g., example01, example15)

Notes

• The visual change across snapshots is consistent: net labels now stand alone where there is no direct connection, matching the expected schematic behavior
• No changes to the net label placement logic itself — only the trace routing decision was fixed

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Project	Deployment	Actions	Updated (UTC)
schematic-trace-solver	Ready	Preview, Comment	May 22, 2026 12:41am