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/app/(admin)/ai/ocr-kombi/page.tsx

@@ -2,7 +2,6 @@
 
 import { Suspense } from 'react'
 import { PagePurpose } from '@/components/common/PagePurpose'
-import { BoxSessionTabs } from '@/components/ocr-pipeline/BoxSessionTabs'
 import { KombiStepper } from '@/components/ocr-kombi/KombiStepper'
 import { SessionList } from '@/components/ocr-kombi/SessionList'
 import { SessionHeader } from '@/components/ocr-kombi/SessionHeader'
@@ -27,8 +26,6 @@ function OcrKombiContent() {
     loadingSessions,
     activeCategory,
     isGroundTruth,
-    subSessions,
-    parentSessionId,
     steps,
     gridSaveRef,
     groupedSessions,
@@ -40,11 +37,8 @@ function OcrKombiContent() {
     deleteSession,
     renameSession,
     updateCategory,
-    handleSessionChange,
     setSessionId,
     setSessionName,
-    setSubSessions,
-    setParentSessionId,
     setIsGroundTruth,
   } = useKombiPipeline()
 
@@ -75,17 +69,11 @@ function OcrKombiContent() {
           <StepPageSplit
             sessionId={sessionId}
             sessionName={sessionName}
-            onNext={() => {
-              // If sub-sessions were created, switch to the first one
-              if (subSessions.length > 0) {
-                setSessionId(subSessions[0].id)
-                setSessionName(subSessions[0].name)
-              }
-              handleNext()
-            }}
-            onSubSessionsCreated={(subs) => {
-              setSubSessions(subs)
-              if (sessionId) setParentSessionId(sessionId)
+            onNext={handleNext}
+            onSplitComplete={(childId, childName) => {
+              // Switch to the first child session and refresh the list
+              setSessionId(childId)
+              setSessionName(childName)
               loadSessions()
             }}
           />
@@ -161,15 +149,6 @@ function OcrKombiContent() {
         onStepClick={handleStepClick}
       />
 
-      {subSessions.length > 0 && parentSessionId && sessionId && (
-        <BoxSessionTabs
-          parentSessionId={parentSessionId}
-          subSessions={subSessions}
-          activeSessionId={sessionId}
-          onSessionChange={handleSessionChange}
-        />
-      )}
-
       <div className="min-h-[400px]">{renderStep()}</div>
     </div>
   )