refactor: add a shared function for tool call & return ids collection.

[StarsExpress]

Refs issue #463 to align repeated tool call & return ids collection.

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Repeated code block

code_puppy/agents/_history.py — prune_interrupted_tool_calls and has_pending_tool_calls:

tool_call_ids: Set[str] = set()
tool_return_ids: Set[str] = set()

for msg in messages:
    for part in getattr(msg, "parts", []) or []:
        kind = _classify_tool_part(part)

        if kind == "call":
            tool_call_ids.add(part.tool_call_id)

        elif kind == "return":
            tool_return_ids.add(part.tool_call_id)

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Extraction

By putting aforementioned repeated code into _collect_tool_ids inside agents/_history.py, prune_interrupted_tool_calls and has_pending_tool_calls both use it to get tool_call_ids and tool_return_ids.