eum.py: ~120 lines of commented-out, half-translated EUM filter API stubs — port or delete

`mikecore/eum.py` carries roughly 120 lines of commented-out, half-translated C# declarations — from about line 1904 to about line 2025 — each carrying a `# TODO: Pending` marker. Nine of the module's TODOs live inside them. They look like this:

```python
# #/
# #/ TODO: Pending
# #/
# @staticmethod
# def eumGetFilterCount(); -> int:
#
# private static bool _eumGetFilterSeq(SeqNo: int, out FtKey: int, out IntPtr lpFtDesc);
```

They are not valid Python even uncommented — the signatures are a mix of Python and C# (`def eumGetFilterCount(); -> int:`, `private static bool`, `out IntPtr`), so they are a transcription of the original API surface rather than code that ever ran.

The affected group is the EUM filter/sequence family (`eumGetFilterCount`, `eumGetFilterSeq`, and neighbours).

Worth deciding once, either way:

- **Port them**, if anything needs to enumerate EUM filters from Python; or
- **Delete them**, and note in the module docstring that the filter API is not wrapped.

Either outcome removes nine TODOs and about 120 lines of noise from the largest module in the package. Leaving them is the only option that keeps implying work is planned when none is.

mikecore/eum.py の 1904–2025 行付近にあるコメントアウトされた EUM フィルター／シーケンスブロックと、その周辺のラップ済み API を調査し、Python の呼び出し元にフィルターの列挙が必要かどうかを判断します。完了条件は、宣言を有効な Python ラッパーに置き換えるか、ブロックとその 9 個の TODOs を削除して、未ラップのフィルター API をモジュール docstring に記載することです。

索引モデルが issue の本文から書いたものです。