Asking to open in a default browser when no browser

`? You need to login to Axiom. Should I open your default browser? `

Frankly it is kinda a dumb question when there is no browser installed (often on containers or VMs or servers, etc). Should check to see if the binaries it is planning to execute exist before prompting the question.

Locate the login prompt and the code that launches the default browser, then inspect how it selects the browser binaries. Verify the available binaries before prompting, and confirm that headless environments no longer receive the browser question while environments with a browser retain the existing flow.

Written by the indexing model from the issue text.