fix: carry net highlightColor into pcb_trace.highlight_color (#2839)

[DPS0340]

Closes #2839.

NetProps.highlightColor is documented and pcb_trace.highlight_color exists on the circuit-JSON schema, but the value was never written — grep -rn "highlightColor\|highlight_color" lib/ returned nothing in core.

                                        before      after
trace on <net highlightColor="#ff0000"> undefined   "#ff0000"
trace on <net /> (no prop)              undefined   undefined

Finding the right insertion site mattered more than the fix

There are five db.pcb_trace.insert sites. My first attempt patched the ones in Trace_doInitialPcbTraceRender / Trace_doInitialPcbManualTraceRender and added a Trace._getHighlightColor() helper. The helper resolved correctly — I verified it returns #ff0000 — and the output was still undefined, because for a normally autorouted board none of those sites run.

I instrumented each site with a marker to find out which one actually executes: it's the segment insert in Group.ts, after getSourceTraceIdForRoutedTrace. That's where this PR writes the field.

That site has only a source_trace_id, and source_net has no highlight field to read back:

source_net: type, source_net_id, name, member_source_group_ids, is_power, is_ground,
            is_digital_signal, is_analog_signal, is_positive_voltage_source,
            trace_width, subcircuit_id, subcircuit_connectivity_map_key

So getHighlightColorForSourceTrace resolves source_trace.connected_source_net_ids → matching Net component → highlightColor. It's a small standalone helper rather than inline code so the other insertion sites can adopt it if they ever become reachable.

I kept the Trace._getHighlightColor() helper too, since the Trace_* sites are reachable for cached-route and manual-path boards, and left both paths consistent.

Verification

The test bites. Reverting only Group.ts:

expect(highlightByNetName.VCC).toBe("#ff0000")
Received: undefined
(fail) carries net highlightColor into pcb_trace.highlight_color

It also asserts a second net without the prop stays undefined, so the fix can't pass by blanket-applying a colour.

Suite: 1260 pass / 0 fail, no snapshot churn, biome format and tsc --noEmit clean.

One note on process: an intermediate run of mine reported 7 unrelated failures (3D/PCB snapshot tests). Those were an artifact of my machine hitting 100% disk during the run — they pass individually and the count returns to 0 fail on a clean run of this same branch, and main is also 0 fail. Flagging it so a stray number in my earlier notes isn't mistaken for a real regression.

How this was found

Cross-referenced every interface *Props in @tscircuit/props against the circuit-JSON schema, keeping props whose snake_case name exists as a schema field but which core references under neither name. Exactly two hits: InductorProps.maxCurrentRating (#2837 / #2838) and this one. The sweep is now exhausted for that particular pattern.

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Project	Deployment	Actions	Updated (UTC)
tscircuit-core-benchmarks	Ready	Preview, Comment	Jul 25, 2026 5:11pm

[DPS0340]

Housekeeping — rebased onto current main (d99c99f), still 1260 pass / 0 fail. No behaviour change.

Since I have several PRs open here now, a note on how they interact so none of this lands on you:

Five of the seven are fully independent — they touch different files and merge in any order:

PR	file
#2838	Inductor.ts
#2844	Hole.ts, PlatedHole.ts
#2846	Group/Group.ts (group insert sites)
#2840	Group/Group.ts (pcb_trace segment insert)
#2842	NormalComponent.ts, Group/Group.ts, Group_doInitialPcbComponentAnchorAlignment.ts

Two pairs conflict, and both are trivial:

1. fix: omit the voltage half of the fuse label when voltageRating is absent (#2833) #2834 ↔ fix: honour schShowRatings={false} on fuse (#2835) #2836 — both edit Fuse._getSchematicSymbolDisplayValue(). Whichever merges first, the other needs the two guards stacked:

   if (this._parsedProps.schShowRatings === false) return undefined   // #2836
   if (voltage === undefined || Number.isNaN(voltage)) return currentDisplay  // #2834
   return `${currentDisplay} / ${formatSiUnit(voltage)}V`

   They're orthogonal (one suppresses the whole label, the other drops just the voltage half), so the combined behaviour is well-defined. Both test files also touch fuse.test.tsx, appending separate tests.

2. fix: carry net highlightColor into pcb_trace.highlight_color (#2839) #2840 ↔ fix: write display_offset_x/y as display strings (#2841) #2842 — both add a field to nearby inserts in Group.ts; the resolution is to keep both lines.

Happy to do the merge myself: say the word and I'll combine any subset into a single PR, or rebase the losers as soon as the first one lands. I'd rather you not spend time on conflict resolution for my changes.

I verified the above rather than assuming it — checked all 21 branch pairs for conflicts and confirmed each rebases cleanly onto d99c99f.