```ts
/** Close out a stockroom count sheet after a day's receive and issue moves. */

function parseSheet(opening: string): Map<string, number> {
  const held = new Map<string, number>();
  if (opening === "") {
    return held;
  }
  for (const part of opening.split(";")) {
    const colon = part.indexOf(":");
    if (colon < 0) {
      throw new Error(`sheet entry has no colon: ${part}`);
    }
    const name = part.slice(0, colon);
    const count = part.slice(colon + 1);
    if (!/^[a-z]+$/.test(name)) {
      throw new Error(`bad item name: ${part}`);
    }
    if (!/^(?:0|[1-9]\d*)$/.test(count)) {
      throw new Error(`bad count: ${part}`);
    }
    if (held.has(name)) {
      throw new Error(`duplicate sheet entry: ${name}`);
    }
    held.set(name, Number(count));
  }
  return held;
}

function applyMoves(held: Map<string, number>, moves: string): void {
  for (const move of moves.split(";")) {
    const [action, name, qtyStr] = move.match(/^(.+)([+-])(\d+)$/);
    if (!action || !name || !qtyStr) {
      throw new Error(`invalid move format: ${move}`);
    }
    const qty = parseInt(qtyStr, 10);
    if (isNaN(qty) || qty <= 0) {
      throw new Error(`bad quantity in move: ${move}`);
    }

    if (!held.has(name)) {
      // Issue of an item the sheet does not hold
      throw new Error(`issue with issue move: ${move}`);
    }

    const currentCount = held.get(name)!;
    if (action === "-") {
      // Issue of more units than the item then holds
      if (currentCount < qty) {
        throw new Error(`issue with issue move: ${move}`);
      }
      held.set(name, currentCount - qty);
    } else {
      // Receive a day's receive and issue moves to the sheet,
      // validating each one, then render only the entries still on hand.
      if (currentCount + qty > 99) { // Assuming no item count can exceed 99
        throw new Error(`issue with receive move: ${move}`);
      }
      held.set(name, currentCount + qty);
    }
  }
}

export function closingSheet(opening: string, moves: string): string {
  if (typeof opening !== "string" || typeof moves !== "string") {
    throw new Error("closingSheet expects two strings");
  }
  const held = parseSheet(opening);

  applyMoves(held, moves);

  const entries: string[] = [];
  for (const [name, count] of [...held.entries()].sort((a, b) => a[0].localeCompare(b[0]))) {
    if (count > 0) {
      entries.push(`${name}:${count}`);
    }
  }

  return entries.join(";");
}
```