fix: redirect root to /demo/

ui: redirect root directly to /demo

Sync with github: Training results and advanced RLVR environment

Sync with github: Training results and advanced RLVR environment

Sync with github: Training results and advanced RLVR environment

feat: ESCTR pivot — Enterprise Supply Chain & Tax Reconciliation

feat: upgrade environment for hackathon finale

Add 2 new frontier-challenging tasks + reward shaping system

Fix: rename start()->main(), add __name__ guard for validator compliance

Restructure project for multi-mode deployment: add uv.lock, openenv-core dependency, server entry point, flat app structure