Refine HsMod.cfg auto-detection for one-click exe usage

[sstxww]

Motivation

• Remove the hardcoded config path so the executable can locate HsMod.cfg automatically.
• Allow an explicit override from the command line while preferring the executable directory and current working directory.
• Avoid broad recursive scanning by using a bounded parent traversal to limit search cost.
• Provide a clear early-exit message when HsMod.cfg cannot be found.

Description

• Replace the hardcoded configFilePath with a call to ResolveConfigPath(args) and early-return when it is null or empty.
• Add ResolveConfigPath, EnumerateCandidatePaths, and FindConfigFileInParents to search in AppContext.BaseDirectory, Directory.GetCurrentDirectory(), and parent directories up to 4 levels.
• Check both HsMod.cfg and BepInEx/config/HsMod.cfg candidates during lookup and prefer the executable directory first via AppContext.BaseDirectory.
• Add using System.Collections.Generic; and simplify the search logic by removing the previous broad recursive enumeration.

Testing

• No automated tests were executed for this change.

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Codex Task