docs: add Hermes Tweet launch handoff

[kriptoburak]

Summary

• Add an optional Hermes Tweet handoff for the Phase 3 X/Twitter launch thread.
• Keep the default distribution flow copy-only unless Hermes Tweet is installed and explicitly gated.
• Mirror the guidance in the Agent H prompt.

Fit and Review

• Target-native fit: this Hermes launch skill already generates X/Twitter launch copy in Phase 3.
• Duplicate check: no open or closed PRs or issues matched Hermes Tweet, Xquik, Twitter, or X/Twitter before opening.
• License reviewed: target repo is MIT; Hermes Tweet is MIT.
• Official Hermes check: verified current Hermes plugin docs and NousResearch/hermes-agent plugin source before opening.

Validation

• git diff --check
• npx --yes markdown-link-check README.md skills/hermes-github-launch/SKILL.md --quiet
• targeted conflict-marker, secret, and unrelated-route scan over touched files