- Create PdfTextToHtml heuristic parser (ALL_CAPS→h2, numbered→h3, bullets→ul, body→p)
- Create document-tabs custom element (ARIA APG tab pattern, roving tabindex, localStorage persistence)
- Register document-tabs element in application.js
- Add tab switcher to submissions/show and submit_form/show when all pages have extracted text
- Add text panel with per-page sections to both views
- Fix role="region" bug on sr-only page text divs (excess ARIA landmarks)
- Add 5 new i18n keys: pdf_view, text_view, document_view_options, text_view_disclaimer, signing_fields_below
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>