Add Hermes Tweet signal skill

[kriptoburak]

Summary

• add a hermes-tweet-signal skill for read-only X/Twitter signal briefs through an installed Hermes Tweet plugin
• update the README and client setup guide so whole-collection installs include the new skill
• document read-only guardrails, required XQUIK_API_KEY setup, and the Hermes Tweet source link

Validation

• reviewed target license: MIT
• checked open and closed PRs/issues for Hermes, Twitter, tweet, and Xquik duplicates: none found
• verified the Hermes Tweet source repository exists and is not archived
• ran git diff --cached --check
• scanned changed files for TweetClaw, provider names, secret values, and private implementation details