Managed GitHub access through a session proxy: standalone proxy support and a failure message

What

In some sessions, Anthropic sets up access to GitHub through a proxy, a go-between server. Both git and gh, the GitHub command-line tool, are routed through it.

• The code that writes the git settings and the gh wrapper can now use a standalone proxy at its own proxyUrl. Before, it always used a local relay at http://127.0.0.1 and a port number.
• The safety checks now also reject a proxy URL that contains a quote or a newline. They already did this for the certificate bundle path.
• A new message covers the case where this access could not be set up because git and gh fail TLS verification against github.com. TLS verification is the check that a secure connection is genuine. The message tells Claude not to turn off TLS verification and not to edit the GIT_CONFIG_GLOBAL file. Instead, Claude should tell you GitHub is unavailable.

Why

Managed GitHub access can work without a local relay. If it breaks, Claude reports the problem instead of weakening connection security to work around it.