Add TweetClaw source context reference

[kriptoburak]

Summary

• add a source-context reference for optional TweetClaw/OpenClaw research inputs
• wire the reference into the research-and-write flow and README reference table
• keep TweetClaw read-only: it supplies public X context, while this skill keeps voice, copy, planning, and publishing decisions

Validation

• git diff whitespace check
• added-line public wording and dash hygiene scan
• markdown-link-check on README, SKILL, research flow, and source context
• SKILL frontmatter check