fix: make getString render ids stable per circuit (#2848)

[DPS0340]

Closes #2848.

Rendering the same board three times in one process produced three different warnings:

before                                    after
<trace#14(from:.R1 > .pin1 to:net.VCC) />  <trace#14(...) />
<trace#36(...) />                          <trace#14(...) />
<trace#58(...) />                          <trace#14(...) />

getString() embeds _renderId, which is a module-level counter that never resets — so the number reflects how many components the process has constructed, not anything about the circuit.

Why the fix is in the display path, not the counter

_renderId has to stay process-unique: cssSelectPrimitiveComponentAdapter compares it for identity (a._renderId === b._renderId). Resetting the counter per circuit would break that. So getString() now offsets against the lowest id in the circuit, computed once and memoised on the root:

_getCircuitRelativeRenderId(): string {
  // walk the tree once, cache the minimum on root._renderIdOrigin
  const relative = Number(this._renderId) - root._renderIdOrigin
  if (!Number.isFinite(relative) || relative < 0) return this._renderId
  return `${relative}`
}

It falls back to the raw id whenever the offset can't be computed (no root yet, non-numeric id, negative result), so no call site can end up worse off than today.

Verification

The test bites. Reverting PrimitiveComponent.ts:

expect(new Set(messages).size).toBe(1)
Expected: 1
Received: 3

A second test guards the obvious way to "fix" this wrongly: ids must stay distinct within a circuit. Two resistors on one board still produce two different strings, so collapsing everything to a constant can't pass.

I also checked that circuits of different shapes still get different numbers (a board with an extra capacitor reports trace#26 vs trace#14) — the id remains meaningful, it just stops depending on process history.

Suite: 1261 pass / 0 fail, tsc --noEmit 0 errors, biome format clean. No snapshots changed.

How this was found

Diffing two renders of an identical board element by element. Of 105 elements, source_unnamed_trace_warning was the only one that differed — which is what pointed at getString() rather than at any single component.

Worth noting the blast radius: getString() also feeds the "routed outside the board boundaries", "chipRef without connections", "manual placement and prop coordinates", "schSheetName does not match", "is ambiguous: references multiple non-overlapping pads", "Missing ports" and "Failed to route net islands" messages. All of them inherit the same instability today.

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Project	Deployment	Actions	Updated (UTC)
tscircuit-core-benchmarks	Ready	Preview, Comment	Jul 25, 2026 5:27pm