Handle LinkedIn auth redirects explicitly

[Antiokh]

Summary

• disable automatic fetch redirect following for LinkedIn API requests
• classify 3xx responses as auth or challenge failures instead of surfacing a generic fetch error
• preserve a clearer redirect error for unexpected locations

Why

LinkedIn can answer Voyager API requests with redirects when a session is expired or challenged. In Node's fetch implementation, automatic redirect following can loop until it fails with
edirect count exceeded, which the CLI was reporting as etch failed. This change makes login and status --verify return actionable auth feedback instead.

Verification

• npm run build
• npm run typecheck
• reproduced etch failed before the change with /voyager/api/me
• after the change, status --verify returns session_valid: false with an auth message instead of a network error