Summary

• Add support for XLBTC as a new collateral branch
• Implement XLBTCPriceFeed contract using Pragma oracle with composite pricing (XLBTC/USD price directly)
• Add dedicated deployment script (deploy_xlbtc_branch.ts) for deploying the XLBTC branch independently
• Configure XLBTC-specific parameters: 125% MCR, 150% CCR, 110% SCR, 10 XLBTC cap, 5%/20% liquidation penalties

Left TODO:

• Deploy new branch using script (linking step has already been commented out)
• Call add_collateral on the Collateral Registry and add_branch_address on USDU.

Test Plan

• Verify XLBTC price feed returns correct composite price from Pragma oracle before linking
• Test trove operations (open, adjust, close) with XLBTC collateral
• Validate liquidation and redemption flows work with new branch