Aligns naming with the convention that "Config" is for file-level configuration
while "Options" and "Settings" describe runtime parameters. Also applies
rustfmt formatting fixes in web_auth.rs.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Add the stripped twin-github test server to the workspace, wire it through
fabro-test, and cover fabro-github's real HTTP auth and pull-request flows
with twin-backed integration tests. This also refactors the GitHub helper
entry points to take explicit base URLs so tests and callers share the same
request path.
