feat: add hermes-tweet skill

[kriptoburak]

Summary

• Add a hermes-tweet research skill for Hermes Agent X/Twitter workflows.
• Document read-first usage, tweet_action approval gates, and secret-handling rules.
• Add the skill to the README research skills table and directory map.

Validation

• git diff --cached --check
• Checked frontmatter and folder-name alignment for .claude/skills/research/hermes-tweet/SKILL.md
• Ran Hermes Tweet public-safety check: checked=35 findings=0
• Ran Hermes Agent compatibility check: official plugin docs reachable and compatibility gate passed

Discovery Notes

• License reviewed: MIT.
• Duplicate check: no existing Hermes Tweet, Xquik, Tweet, Twitter, or social PRs/issues in this repo.
• Safety check: no credentials, private implementation details, or direct HTTP fallback instructions added.