docs(repo): Retry GitHub CLI outside the sandbox

[kyleve]

Posted by an AI agent on kve’s behalf.

Summary

• teach local GitHub workflows to retry sandboxed authentication failures with narrowly scoped escalation
• reuse escalation for the remaining GitHub commands after Keychain-backed authentication succeeds

Why

Sandboxed gh probes can incorrectly report missing or invalid authentication because the macOS Keychain credential is unavailable inside the sandbox. The new rule avoids unnecessary login requests and repeated failed probes.

Verification

• ./sync-agents
• git diff --check
• generic skill validator attempted, but its Python environment does not include PyYAML
• ./test not run because this is a Markdown-only agent-guidance change