Add Hermes Tweet plugin

[kriptoburak]

Adds Hermes Tweet as a Claude Code marketplace plugin for Hermes Agent X/Twitter research workflows.

Changes:

• Registers hermes-tweet in .claude-plugin/marketplace.json.
• Adds plugins/hermes-tweet with plugin metadata, README, and a routing skill.
• Documents the plugin in the README plugin list.

Validation:

• python3 -m json.tool .claude-plugin/marketplace.json
• python3 -m json.tool plugins/hermes-tweet/plugin.json
• claude plugin validate .
• pnpm vitest run src/tests/integration/marketplace-sync.test.ts
• git diff --check
• curl -fsSLI https://github.com/Xquik-dev/hermes-tweet