feat(cad): iterate on failing KCL in retries and add Zoo engine prompt guardrails

[devin-ai-integration]

Summary

Cuts the dominant cost in long text_to_cad runs: a self-heal retry used to call cad.textToCad again with an empty main.kcl, so Zoo rewrote the whole part from scratch (the ~15-minute rear_cover retry in the analyzed logs). Retries now patch the failing script instead, and every prompt carries guardrails for the engine limits Zoo's model keeps hitting.

• text_to_cad retry path in tools.ts:

  attempt > 1 && lastKcl
    ? cad.iterateCad(lastKcl, buildFixIteratePrompt(job.prompt, lastError))   // edit_kcl_code — patch the failing file
    : cad.textToCad(attempt > 1 ? buildRegeneratePrompt(...) : withKclGuardrails(job.prompt))
  

  lastKcl is captured when engine verification fails; generation-level failures (no KCL produced) still regenerate.
• New apps/web/lib/cad/zoo-guardrails.ts — KCL_ENGINE_GUARDRAILS appended to all generation prompts:
  • no boolean union()/subtract() of separate solids (model one closed-profile extrusion, cut from it) — matches the The Zoo engine cannot handle this 3D union/subtraction yet failures;
  • point() takes no construction argument — a recurring model hallucination.

Tests

• zoo-guardrails.test.ts covers withKclGuardrails, buildRegeneratePrompt, buildFixIteratePrompt.
• pnpm --filter @foundry/web test (484), lint, typecheck, format all pass.

Link to Devin session: https://app.devin.ai/sessions/d846e91524fc43aca04de9649aeb2300
Requested by: @alanshen27

[devin-ai-integration]

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