docs: add TweetClaw as an X/Twitter monitoring source

[kriptoburak]

Summary

• add TweetClaw as an optional OpenClaw X/Twitter data source in the social-media-monitor skill
• update the README monitoring table so sellers can find the X/Twitter evidence path
• keep credentials in private OpenClaw config and require approval for write-capable TweetClaw actions

Validation

• git diff --check
• added-line dash and sensitive-value scans
• touched-file link sweep: 19 unique external links, 107 local links, 0 unexpected failures
• frontmatter check for social-media-monitor/SKILL.md
• python3 -m py_compile brand-monitoring/scripts/monitor.py brand-monitoring/scripts/scrapers.py
• npm view @xquik/tweetclaw version -> 1.6.31