feat: Full-Row OCR mit Spacing fuer Box-Sub-Sessions

Sub-Sessions ueberspringen Spaltenerkennung und nutzen stattdessen eine
Pseudo-Spalte ueber die volle Breite. Text wird mit proportionalem
Spacing aus Wort-Positionen rekonstruiert, um raeumliches Layout zu erhalten.

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

admin-lehrer/components/ocr-pipeline/StepColumnDetection.tsx

@@ -45,6 +45,7 @@ export function StepColumnDetection({ sessionId, onNext, onBoxSessionsCreated }:
   const [savedGtColumns, setSavedGtColumns] = useState<PageRegion[] | null>(null)
   const [creatingBoxSessions, setCreatingBoxSessions] = useState(false)
   const [existingSubSessions, setExistingSubSessions] = useState<SubSession[] | null>(null)
+  const [isSubSession, setIsSubSession] = useState(false)
 
   // Fetch session info (image dimensions) + check for cached column result
   useEffect(() => {
@@ -58,14 +59,31 @@ export function StepColumnDetection({ sessionId, onNext, onBoxSessionsCreated }:
           if (info.image_width && info.image_height) {
             setImageDimensions({ width: info.image_width, height: info.image_height })
           }
+          const isSub = !!info.parent_session_id
+          setIsSubSession(isSub)
           if (info.sub_sessions && info.sub_sessions.length > 0) {
             setExistingSubSessions(info.sub_sessions)
             onBoxSessionsCreated?.(info.sub_sessions)
           }
           if (info.column_result) {
             setColumnResult(info.column_result)
+            // Sub-session with pseudo-column already set → auto-advance
+            if (isSub) {
+              onNext()
+              return
+            }
             return
           }
+          // Sub-session without columns → auto-detect (creates pseudo-column)
+          if (isSub) {
+            const res = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}/columns`, { method: 'POST' })
+            if (res.ok) {
+              const data: ColumnResult = await res.json()
+              setColumnResult(data)
+              onNext()
+              return
+            }
+          }
         }
       } catch (e) {
         console.error('Failed to fetch session info:', e)