Function decisionOf

src/ui-server/api/steps.ts:659–672

(guards: readonly BranchGuard[])

   * share, so it is the innermost that says which way this site went.
   */
  const decisionOf = (guards: readonly BranchGuard[]): WireStepDecision | null => {
    const g = guards[guards.length - 1];
    if (!g || !g.branch) return null;
    // A one-sided guard (`if (!product) throw`) is a guard clause, not a
    // choice with two drawn ways; it keeps its condition on the line.
    if (g.form === 'guard') return null;
    return {
      branch: g.branch,
      on: guardLabel([{ ...g, negated: false }]),
      arm: guardLabel([g]),
      form: g.form === 'case' ? 'switch' : g.form === 'ternary' ? 'ternary' : g.form === 'catch' ? 'try' : 'if',
      ...(g.negated ? { not: true as const } : {}),
    };
  };

  const steps = new Map<string, StepRecord>();
  const links = new Map<string, WireStepLink>();