include(), read(), etc within a file use a different base directory when called from cmdline/MC VS interpreter

This topic was discussed on Discord, this issue serves the purpose of not losing the results.

## Desired behavior
- MC: Relative to script directory (no change).
- Cmdline: Relative to script directory.
- Interpreter/MC interpreter:
- Functions entered directly into the interpreter use the directory set using `cd()` as base directory.
- Included MS files (including the procedures defined within them) use their parent directory as base directory (same behavior as non-interpreter mode).
- Procedures defined in the interpreter use the directory set using `cd()` at definition time for all calls to that procedure.

まず、cmdline、MC interpreter、interpreter モードでの相対パスの動作を再現し、次に include()、read()、cd() の処理と、スクリプトまたはプロンプトで定義されたプロシージャの処理を追跡します。Desired behavior に記載されたベースディレクトリを各ケースが使用し、定義後に呼び出されるプロシージャも含まれていれば完了です。

索引モデルが issue の本文から書いたものです。