```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

    held = parse_sheet(opening)
    # TODO: apply the day's semicolon-separated moves to the sheet,
    # validating each one, then render only the entries still on hand.
    entries = []
    for move in moves.split(";"):
        parts = move.split("+")
        if len(parts) != 2:
            raise ValueError(f"move does not contain exactly two parts: {move}")
        name, qty_str = parts
        if re.fullmatch(r"[a-z]+", name) is None:
            raise ValueError(f"bad item name in move: {move}")
        if re.fullmatch(r"0|[1-9]\d*", qty_str) is None:
            raise ValueError(f"bad count in move: {move}")
        qty = int(qty_str)
        if name not in held:
            raise ValueError(f"item {name} is not on the sheet")
        if held[name] < qty:
            raise ValueError(f"cannot issue {qty} units of {name} from the sheet")
        held[name] -= qty
        if held[name] == 0:
            entries.append(f"{name}:0")
        else:
            entries.append(f"{name}:{held[name]}")
    entries.sort()
    return ";".join(entries)
```