refactor(report): consolidate 27 render helpers into render_helpers.py

feat(sprint-A6): WCAG niveau A bloquant — skip-link, canvas a11y, scope=col

refactor(report): regrouper renderers depuis extras/render/

fix(ci): restaurer rétrocompat tests + corriger 14 cassures CI

phaseB: extras/historical/ — 8 modules philologiques + 2 renderers en Cercle 3

sprint80: sur-normalisation lexicale (A.I.7 couche calcul + HTML)