Remove Hauptseite/Box tabs from Kombi pipeline

Page-split now creates independent sessions that appear directly in
the session list. After split, the UI switches to the first child
session. BoxSessionTabs, sub-session state, and parent-child tracking
removed from Kombi code. Legacy ocr-overlay still uses BoxSessionTabs.

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

admin-lehrer/components/ocr-kombi/StepPageSplit.tsx

@@ -1,8 +1,6 @@
 'use client'
 
 import { useState, useEffect, useRef } from 'react'
-import type { SubSession } from '@/app/(admin)/ai/ocr-pipeline/types'
-
 const KLAUSUR_API = '/klausur-api'
 
 interface PageSplitResult {
@@ -18,10 +16,10 @@ interface StepPageSplitProps {
   sessionId: string | null
   sessionName: string
   onNext: () => void
-  onSubSessionsCreated: (subs: SubSession[]) => void
+  onSplitComplete: (firstChildId: string, firstChildName: string) => void
 }
 
-export function StepPageSplit({ sessionId, sessionName, onNext, onSubSessionsCreated }: StepPageSplitProps) {
+export function StepPageSplit({ sessionId, sessionName, onNext, onSplitComplete }: StepPageSplitProps) {
   const [detecting, setDetecting] = useState(false)
   const [splitResult, setSplitResult] = useState<PageSplitResult | null>(null)
   const [error, setError] = useState('')
@@ -40,30 +38,33 @@ export function StepPageSplit({ sessionId, sessionName, onNext, onSubSessionsCre
     setDetecting(true)
     setError('')
     try {
-      // First check if sub-sessions already exist
+      // First check if this session was already split (status='split')
       const sessionRes = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions/${sessionId}`)
       if (sessionRes.ok) {
         const sessionData = await sessionRes.json()
-        if (sessionData.sub_sessions?.length > 0) {
-          // Already split — show existing sub-sessions
-          const subs = sessionData.sub_sessions as { id: string; name: string; page_index?: number; box_index?: number; current_step?: number }[]
-          setSplitResult({
-            multi_page: true,
-            page_count: subs.length,
-            sub_sessions: subs.map((s: { id: string; name: string; page_index?: number; box_index?: number }) => ({
-              id: s.id,
-              name: s.name,
-              page_index: s.page_index ?? s.box_index ?? 0,
-            })),
-          })
-          onSubSessionsCreated(subs.map((s: { id: string; name: string; page_index?: number; box_index?: number; current_step?: number }) => ({
-            id: s.id,
-            name: s.name,
-            box_index: s.page_index ?? s.box_index ?? 0,
-            current_step: s.current_step ?? 2,
-          })))
-          setDetecting(false)
-          return
+        if (sessionData.status === 'split' && sessionData.crop_result?.multi_page) {
+          // Already split — find the child sessions in the session list
+          const listRes = await fetch(`${KLAUSUR_API}/api/v1/ocr-pipeline/sessions`)
+          if (listRes.ok) {
+            const listData = await listRes.json()
+            // Child sessions have names like "ParentName — Seite N"
+            const baseName = sessionName || sessionData.name || ''
+            const children = (listData.sessions || [])
+              .filter((s: { name?: string }) => s.name?.startsWith(baseName + ' — '))
+              .sort((a: { name: string }, b: { name: string }) => a.name.localeCompare(b.name))
+            if (children.length > 0) {
+              setSplitResult({
+                multi_page: true,
+                page_count: children.length,
+                sub_sessions: children.map((s: { id: string; name: string }, i: number) => ({
+                  id: s.id, name: s.name, page_index: i,
+                })),
+              })
+              onSplitComplete(children[0].id, children[0].name)
+              setDetecting(false)
+              return
+            }
+          }
         }
       }
 
@@ -92,12 +93,8 @@ export function StepPageSplit({ sessionId, sessionName, onNext, onSubSessionsCre
           sub.name = newName
         }
 
-        onSubSessionsCreated(data.sub_sessions.map(s => ({
-          id: s.id,
-          name: s.name,
-          box_index: s.page_index,
-          current_step: 2,
-        })))
+        // Signal parent to switch to the first child session
+        onSplitComplete(data.sub_sessions[0].id, data.sub_sessions[0].name)
       }
     } catch (e) {
       setError(e instanceof Error ? e.message : String(e))