Function traceStep

src/compute-engine/boxed-expression/solve.ts:80–86

Record one narrative step. `value` is the equation state after the step.

(
  trace: RuleSteps | undefined,
  because: string,
  value: Expression
)

  const val = numericValue(ratio);
  if (val === undefined) return undefined;
  if (typeof val === 'number') return val;
  if (val.im !== 0) return undefined;
  return val.re;
}

/**
 * Producer-side chokepoint for a validity-guarded root (conditional-values
 * design, decision 7). Resolves a *decidable* guard against evaluation + the
 * assumption store:
 *   - guard evaluates to `True`  → the bare `root` (guard discharged);