Fix auth-required error message and replace jcsalterego examples
- lib/respond.ts: detect AuthRequired (401) errors and return a friendly
markdown notice instead of a raw error response
- app/cli/route.ts: fix /feed → /posts in examples; replace jcsalterego
with mackuba.eu; add note about private accounts
- app/page.tsx: replace jcsalterego with mackuba.eu in terminal section;
fix /feed → /posts example path
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>