Bug: tilde `~` path does not work on macOS

I've shared the configuration of WindTerm between multiple computers with different OS.

Then I want to make the SSH key path be same.

For now, `~/.ssh/id_rsa` works fine on Linux and even Windows, but not on macOS.

It's already reported at #872 but stale for a long time.

Could someone please pay a bit of attention to the issue? It's really important for me.

Reproduce the SSH key path issue on macOS using `~/.ssh/id_rsa`, then trace where configured paths are parsed and expanded. Compare the behavior with Linux and Windows, and consider issue #872 for prior context; done means the same shared path resolves correctly on macOS without breaking the other platforms.

Written by the indexing model from the issue text.