```python
"""Close out a stockroom count sheet after a day's receive and issue moves."""

import re


def closing_sheet(opening: str, moves: str) -> str:
    if not isinstance(opening, str) or not isinstance(moves, str):
        raise ValueError("closing_sheet expects two strings")

    def parse_sheet(text):
        held = {}
        if text == "":
            return held
        for part in text.split(";"):
            name, colon, count = part.partition(":")
            if colon == "":
                raise ValueError(f"sheet entry has no colon: {part}")
            if re.fullmatch(r"[a-z]+", name) is None:
                raise ValueError(f"bad item name: {part}")
            if re.fullmatch(r"0|[1-9]\d*", count) is None:
                raise ValueError(f"bad count: {part}")
            if name in held:
                raise ValueError(f"duplicate sheet entry: {name}")
            held[name] = int(count)
        return held

    def apply_move(held, move):
        if not isinstance(move, str):
            raise ValueError("move must be a string")
        parts = move.split("+", "-")
        if len(parts) != 2:
            raise ValueError(f"invalid move format: {move}")
        name, qty_str = parts
        if re.fullmatch(r"[a-z]+", name) is None:
            raise ValueError(f"bad item name in move: {move}")
        try:
            qty = int(qty_str)
        except ValueError:
            raise ValueError(f"invalid quantity in move: {move}")
        if name not in held:
            if qty == 0:
                return
            raise ValueError(f"issue of non-existent item: {move}")
        if held[name] < qty:
            raise ValueError(f"issue more than available: {move}")
        held[name] -= qty

    held = parse_sheet(opening)
    for move in moves.split(";"):
        apply_move(held, move)

    entries = []
    for name in sorted(held):
        if held[name] > 0:
            entries.append(f"{name}:{held[name]}")
    return ";".join(entries)
```