docs: add TweetClaw source companion

[kriptoburak]

Summary

• Document TweetClaw as an optional OpenClaw companion for X source research before this skill posts through the browser flow.
• Add approval and secret-handling boundaries for TweetClaw, browser, monitor, webhook, extraction, media, DM, and posting actions.
• Keep this skill's browser automation path as the default publishing route.

Validation

• git diff --check
• Added-line public hygiene scan for stale handles, secret-like names, and unsafe wording
• Local docs assertion for pinned TweetClaw install and approval text
• curl link checks for the TweetClaw GitHub repository and npm registry metadata