fix(shell): hint when github auth is missing for state sync

[skulidropek]

Closes #163

Summary

• detect GitHub HTTPS remotes that embed a username and normalize them to a canonical GitHub URL
• show a clear GitHub re-auth hint for state sync, pull and push when GitHub auth is missing or a GitHub fetch fails
• split state repo local/pull-push/auth-hint helpers into smaller modules and add regression coverage for the new GitHub auth helpers

Verification

• pnpm check
• pnpm lint
• pnpm lint:effect
• pnpm build
• pnpm test