Fixes bug deleting chat file when config.chat_dir contains a symlink

[Odie]

The Bug

When deleting a chat, if any path component in config.chat_dir is a symlink, the following sanity check fails:

	if not _H.starts_with(file_name, M.config.chat_dir) then
		M.logger.warning("File " .. vim.inspect(file_name) .. " is not in chat dir")
		return
	end

This causes the GpChatDelete command to always fail in such cases.

The fix

Resolve chat_dir symlinks when performing the sanity check.

[Odie]

It might be a good idea to have a helper function to always retrieve the resolved version of config.chat_dir. Alternatively, it's also possible to just resolve the config.chat_dir during setup. Either case, it should make these kinds of bugs very unlikely to show up. =)