Write #start-here and #verify pinned guides

[skylessdev]

Scope

• Welcome message: official links, phishing warning, “what the 💎shapeℱ tag means,” verify instructions.
• Short FAQ: “What if my score is stale?”, “How to unlink?”, “Thresholds?”
• Include Discord vanity link + website + GitHub.

Acceptance Criteria

• Pinned message in #start-here + #verify.
• Links to official site and GitHub are correct.
• Clear warning: tag is cosmetic; roles are the trust signal.