[WINDOWS 10] proxy_ca_certs : The system cannot find the path specified.

I encountered a bug while trying to use Keybase behind a corporate proxy, and trying to configure the proxy_ca_certs.

```powershell
keybase config set proxy_ca_certs $HOME\Downloads\proxy-ca.pem # OK
keybase config get proxy_ca_certs # OK, returns a quoted path like "C:\\Users\\John\\Downloads\\proxy-ca.pem"
```

```powershell
keybase login # ERROR
- ERROR Failed to configure API access: In config file C: open C: The system cannot find the file specified.
```

I tried to escape the path, replacing with `/`, use `$HOME`, without success.

Start by reproducing the PowerShell commands for proxy_ca_certs and the subsequent keybase login failure. Trace how the configured Windows path is read when API access is initialized; done means login successfully loads the certificate path without the “C:” file-not-found error.

Written by the indexing model from the issue text.