Check PCB trace maximum lengths during routing DRC

[seveibar]

Summary

• add a generic routing check that compares each pcb_trace length with its source trace's max_length
• emit pcb_trace_too_long_warning through runAllRoutingChecks
• use a routed trace's recorded trace_length when available and compute it from route points otherwise
• ignore absent or null maximum lengths

Architecture

This check deliberately has no crystal-specific logic. Core is responsible for teeing up Circuit JSON by assigning component-derived limits to source_trace.max_length; the normal routing DRC pipeline is responsible for producing warnings.

Companion: tscircuit/core#2781

Validation

• bun test (132 passing)
• bunx tsc --noEmit
• bun run build
• Biome and git diff --check pass

[graphite-app]

This file contains two test(...) calls (lines 54 and 72), which violates the rule that a *.test.ts file may have AT MOST one test(...). Please split this into two separate numbered files, e.g. check-pcb-trace-lengths1.test.ts (for the 'warns when a PCB trace exceeds its source trace maximum length' test) and check-pcb-trace-lengths2.test.ts (for the 'is included in the routing check pipeline' test).

Spotted by Graphite (based on custom rule: Custom rule)



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[graphite-app]

Critical bug: The continue statement skips calculating the distance from the via to the next route point. This causes traces with vias to report shorter lengths than actual, potentially missing length violations.

Impact: Traces containing vias will have their lengths underreported by the distance between the via and the next route point, causing the check to miss traces that actually exceed their maximum length.

Fix: Remove the continue statement and let the code fall through to calculate the distance to the next point:

if (routePoint.route_type === "via") {
  traceLength += DEFAULT_VIA_LENGTH_MM
  // Don't continue - still need to calculate distance to next point
}

Suggested change

	if (routePoint.route_type === "via") {
	traceLength += DEFAULT_VIA_LENGTH_MM
	continue
	}
	if (routePoint.route_type === "via") {
	traceLength += DEFAULT_VIA_LENGTH_MM
	// Don't continue - still need to calculate distance to next point
	}

Spotted by Graphite



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[tscircuitbot]

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Thank you for your contribution! 🎉

PR Rating: ⭐⭐
Impact: Minor

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