feat(ui): add PDF export via browser print

Adds a PDF button to the report header. Clicking it opens
/chart/current?print=true in a new tab, which auto-triggers
window.print() so the user can save to PDF via the browser dialog.

- chart submodule bumped: PrintMode support (no filter JS, auto-print,
  @media print CSS)
- handlers.go: passes PrintMode=true when ?print=true query param is set
- index.html: PDF button alongside Raw Data / Reanimator
- app.js: printReport() helper; button shown/hidden with other exports

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bible-local/07-exporters.md

@@ -7,6 +7,7 @@
 | `GET /api/export/csv` | CSV | Serial-number export |
 | `GET /api/export/json` | raw-export ZIP bundle | Reopen and re-analyze later |
 | `GET /api/export/reanimator` | JSON | Reanimator hardware payload |
+| `GET /chart/current?print=true` | HTML (auto-print) | Print/PDF version of the report — opens in new tab, calls `window.print()` |
 | `POST /api/convert` | async ZIP artifact | Batch archive-to-Reanimator conversion |
 
 ## Raw export