Seven new timeline_* keys feeding the upcoming chrome: the header meta
line (grouping label + events count), the event-pill provenance token,
the ✉ sr-only label, the world-band "historisch" suffix, and the strip
density caption — present in de/en/es with matching key sets, pinned by a
new parity test.
Refs #833
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
REQ-024 was updated (issue #779) to require localized sr-only/aria
labels instead of German-only. Pin the de/en/es values so they cannot
silently drift back to the German source strings.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Adds 7 Paraglide keys (viewer_previous_page, viewer_next_page,
viewer_zoom_out, viewer_zoom_in, transcribe_mark_for_training,
layout_menu_open, layout_menu_close) to de/en/es.json.
Adds messages.spec.ts to enforce key parity across all three locales.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
