fix(code): align relay connect with fleet workspace

[danii1]

Summary

• save verified GitHub relay pairing into the fleet workspace when devintern worker connect github is run from a managed repository
• reuse the repository-local sign-in session while writing the connection state the worker actually reads
• preserve central-App routing for live legacy repo registrations, forcing token-only GitHub API auth and injecting the devintern-ai mention alias
• document the repository-first repair flow and add regression coverage

Verification

• pre-commit format, lint, and typecheck passed
• pre-push monorepo test and typecheck passed
• @getdevintern/code: 1287 passed, 0 failed
• production code-package build passed