fix(#240): align Mission Control Strip UI with final spec

- Strip heading: "Mitarbeiten" → "Was braucht Aufmerksamkeit?"
- Column 1 heading: "Segmentierung" → "Rahmen einzeichnen"; add green
  skill pill "✓ Ohne Vorkenntnisse"; heading color gray → ink (navy)
- Column 2 heading: "Transkription" → "Text eintippen"; add navy skill
  pill "Kurrent hilfreich"; heading color gray → ink; weekly pulse
  color green → ink (task, not achievement); progress bar track
  bg-gray-200/h-1.5 → bg-ink/20/h-1; add transition-all to fill
- Column 3 heading: "Lesefertig" → "Lesefertig ✓"; heading color
  gray → green-800; add "N Dokumente bereit" subtitle in green; add
  "Alle N lesen →" link at bottom; reviewed % color gray → green-800
- All columns: add CTA buttons at bottom (Jetzt einzeichnen /
  Jetzt tippen); empty state removed from cols 1 & 2 (columns
  hide when empty); empty-state ghost CTA in col 3 restyled as
  bordered button with hover:bg-ink
- Strip: add visibility guard — hides when all three lists are empty
- i18n: add mission_control_seg_skill_pill, mission_control_trans_skill_pill,
  mission_control_ready_subtitle, mission_control_ready_all_cta in
  de/en/es; update heading and CTA copy in all three locales

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

frontend/messages/de.json

@@ -556,17 +556,21 @@
 	"transcription_block_segmentation_only": "Nur Segmentierung",
 	"training_chip_kurrent": "Kurrent-Erkennung",
 	"training_chip_segmentation": "Segmentierung",
-	"mission_control_heading": "Mitarbeiten",
-	"mission_control_segmentation_heading": "Segmentierung",
+	"mission_control_heading": "Was braucht Aufmerksamkeit?",
+	"mission_control_segmentation_heading": "Rahmen einzeichnen",
 	"mission_control_segmentation_description": "Textbereiche markieren — keine Vorkenntnisse nötig",
-	"mission_control_segmentation_cta": "Segmentieren",
+	"mission_control_seg_skill_pill": "✓ Ohne Vorkenntnisse",
+	"mission_control_segmentation_cta": "Jetzt einzeichnen →",
 	"mission_control_segmentation_empty": "Alle Dokumente haben bereits Segmentierungsblöcke.",
-	"mission_control_transcription_heading": "Transkription",
+	"mission_control_transcription_heading": "Text eintippen",
 	"mission_control_transcription_description": "Text abschreiben — Kurrent-Kenntnisse hilfreich",
-	"mission_control_transcription_cta": "Transkribieren",
+	"mission_control_trans_skill_pill": "Kurrent hilfreich",
+	"mission_control_transcription_cta": "Jetzt tippen →",
 	"mission_control_transcription_empty": "Keine Dokumente warten auf Transkription.",
-	"mission_control_ready_heading": "Lesefertig",
+	"mission_control_ready_heading": "Lesefertig ✓",
 	"mission_control_ready_description": "Vollständig transkribiert und geprüft",
+	"mission_control_ready_subtitle": "{count} Dokumente bereit",
+	"mission_control_ready_all_cta": "Alle {count} lesen →",
 	"mission_control_ready_empty": "Noch keine Dokumente vollständig transkribiert.",
 	"mission_control_ready_empty_cta": "Jetzt mitmachen",
 	"mission_control_weekly_pulse": "↑ +{count} diese Woche",

frontend/messages/en.json

@@ -556,17 +556,21 @@
 	"transcription_block_segmentation_only": "Segmentation only",
 	"training_chip_kurrent": "Kurrent recognition",
 	"training_chip_segmentation": "Segmentation",
-	"mission_control_heading": "Contribute",
-	"mission_control_segmentation_heading": "Segmentation",
+	"mission_control_heading": "What needs attention?",
+	"mission_control_segmentation_heading": "Draw regions",
 	"mission_control_segmentation_description": "Mark text areas — no prior knowledge needed",
-	"mission_control_segmentation_cta": "Segment",
+	"mission_control_seg_skill_pill": "✓ No prior knowledge",
+	"mission_control_segmentation_cta": "Start marking →",
 	"mission_control_segmentation_empty": "All documents already have segmentation blocks.",
-	"mission_control_transcription_heading": "Transcription",
+	"mission_control_transcription_heading": "Type the text",
 	"mission_control_transcription_description": "Type out text — Kurrent knowledge helpful",
-	"mission_control_transcription_cta": "Transcribe",
+	"mission_control_trans_skill_pill": "Kurrent helpful",
+	"mission_control_transcription_cta": "Start typing →",
 	"mission_control_transcription_empty": "No documents waiting for transcription.",
-	"mission_control_ready_heading": "Ready to Read",
+	"mission_control_ready_heading": "Ready to read ✓",
 	"mission_control_ready_description": "Fully transcribed and reviewed",
+	"mission_control_ready_subtitle": "{count} documents ready",
+	"mission_control_ready_all_cta": "Read all {count} →",
 	"mission_control_ready_empty": "No documents fully transcribed yet.",
 	"mission_control_ready_empty_cta": "Start contributing",
 	"mission_control_weekly_pulse": "↑ +{count} this week",

frontend/messages/es.json

@@ -556,17 +556,21 @@
 	"transcription_block_segmentation_only": "Solo segmentación",
 	"training_chip_kurrent": "Reconocimiento Kurrent",
 	"training_chip_segmentation": "Segmentación",
-	"mission_control_heading": "Colaborar",
-	"mission_control_segmentation_heading": "Segmentación",
+	"mission_control_heading": "¿Qué necesita atención?",
+	"mission_control_segmentation_heading": "Marcar regiones",
 	"mission_control_segmentation_description": "Marcar áreas de texto — sin conocimientos previos",
-	"mission_control_segmentation_cta": "Segmentar",
+	"mission_control_seg_skill_pill": "✓ Sin conocimientos previos",
+	"mission_control_segmentation_cta": "Empezar a marcar →",
 	"mission_control_segmentation_empty": "Todos los documentos ya tienen bloques de segmentación.",
-	"mission_control_transcription_heading": "Transcripción",
+	"mission_control_transcription_heading": "Escribir el texto",
 	"mission_control_transcription_description": "Escribir el texto — conocimiento de Kurrent útil",
-	"mission_control_transcription_cta": "Transcribir",
+	"mission_control_trans_skill_pill": "Kurrent útil",
+	"mission_control_transcription_cta": "Empezar a escribir →",
 	"mission_control_transcription_empty": "No hay documentos esperando transcripción.",
-	"mission_control_ready_heading": "Listo para leer",
+	"mission_control_ready_heading": "Listo para leer ✓",
 	"mission_control_ready_description": "Completamente transcrito y revisado",
+	"mission_control_ready_subtitle": "{count} documentos listos",
+	"mission_control_ready_all_cta": "Leer todos ({count}) →",
 	"mission_control_ready_empty": "Aún no hay documentos completamente transcritos.",
 	"mission_control_ready_empty_cta": "Empezar a colaborar",
 	"mission_control_weekly_pulse": "↑ +{count} esta semana",