Auto-guarantee escrow for marketplace deals

Every paid strategy in the marketplace now ships with an automatic escrow guarantee. Buyers get a structured safety net without needing a human arbitrator for common cases.

• 7-day trial window — buyer can open a dispute for "does not match description" or "strategy does not run"
• Auto-release — if no dispute is filed within the window, funds release to the seller
• Dispute flow — simple two-sided evidence form, resolved within 72h
• Seller stake — marketplace holds 5% of the listing price as a reputation bond until the trial window closes

Disputes that require human review get escalated to the moderator queue; the moderator's decision is logged against the seller's profile and visible to future buyers.