chore(sync): mirror front-door files to Space (hf-sync)

sync drifted files from GitHub main canonical (governance.html, fabric.js, governance.js) — reconcile HF Space to current main

Dev B: add governance source files missing on Space (tau eval, IETF receipt view, Colang ROE policy, /governance page, Lean4Agent scaffold) — byte-identical to GitHub; fixes Dockerfile COPY cache-miss build error