```ts
/** Fixed-point money helpers: parse, format, and allocate integer cents. */

export function parseAmount(text: string): number {
  if (typeof text !== "string") {
    throw new Error("amount must be a string");
  }
  const match = /^(\d+)(?:\.(\d{2}))?$/.exec(text);
  if (match === null) {
    throw new Error(`malformed amount: ${text}`);
  }
  const whole = Number(match[1]);
  const cents = match[2] === undefined ? 0 : Number(match[2]);
  return whole * 100 + cents;
}

export function formatAmount(cents: number): string {
  if (!Number.isInteger(cents) || cents < 0) {
    throw new Error("cents must be a non-negative integer");
  }
  const whole = Math.floor(cents / 100);
  const rest = String(cents % 100).padStart(2, "0");
  return `${whole}.${rest}`;
}

export function allocateCents(totalCents: number, weights: number[]): number[] {
  if (weights.length === 0) {
    throw new Error("weight list must not be empty");
  }
  for (const weight of weights) {
    if (!Number.isInteger(weight) || weight < 0) {
      throw new Error("all weights must be non-negative integers");
    }
  }
  const sum = weights.reduce((acc, weight) => acc + weight, 0);
  if (sum === 0) {
    return Array(totalCents).fill(0);
  }

  let leftover = totalCents;
  const shares: number[] = [];

  for (const weight of weights.sort((a, b) => b - a)) {
    const share = Math.floor(leftover * weight / sum);
    shares.push(share);
    leftover -= share;
  }

  return shares;
}
```