cornerstone-data/bedrock: v0.1 of merged USEEIO and CEDA-US model

What's Changed ### Core Pipeline Added Cornerstone 2026 model schema with sector mappings and config gating Built EEIO pipeline: B matrix with industry output year adjustment and scrap adjustment Integrated FLOWSA for flow-by-activity/sector generation GHG Emissions Updated GHG attribution across electricity, natural gas, petroleum, mobile combustion, refrigerants, and agricultural sources Aligned allocation methods (enteric fermentation, manure management, liming) with FLOWSA Added CEDA GHG as FBS method Waste Disaggregation Implemented full waste disaggregation pipeline (config, weight loader, IO table disagg, pipeline integration) Diagnostics & Validation Created diagnostics module: emission factors, national accounting balance, sector-level comparisons Added config-driven baseline snapshots with GCS storage Built Google Sheets integration for diagnostics output Infrastructure Reorganized codebase from ceda_usa/ into extract/, transform/, utils/ modules Added mypy CI across all modules, resolved type annotations project-wide Set up integration test GHA with cron scheduling Added Cornerstone sector schema, MECS mappings, and E matrix expansion New Contributors @cclin130, @danfrankj, @michaelsteffen, @catherinebirney, @jvendries, @briantobin-99, @WesIngwersen Full Changelog: https://github.com/cornerstone-data/bedrock/commits/v0.1