fix: deduplicate overlapping OCR words and use per-word Y positions in overlay

Backend: Add spatial overlap check (>=50% horizontal IoU) to Kombi merge
so words at the same position are deduplicated even when OCR text differs.

Frontend: Add yPct/hPct to WordPosition so each word renders at its actual
vertical position instead of all words collapsing to the cell center Y.

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

admin-lehrer/components/ocr-overlay/OverlayReconstruction.tsx

@@ -513,9 +513,9 @@ export function OverlayReconstruction({ sessionId, onNext }: OverlayReconstructi
                         className="absolute leading-none pointer-events-none select-none"
                         style={{
                           left: `${wp.xPct}%`,
-                          top: `${bboxPct.y}%`,
+                          top: `${wp.yPct}%`,
                           width: `${wp.wPct}%`,
-                          height: `${bboxPct.h}%`,
+                          height: `${wp.hPct}%`,
                           fontSize: `${fs}px`,
                           fontWeight: globalBold ? 'bold' : 'normal',
                           fontFamily: "'Liberation Sans', Arial, sans-serif",
@@ -534,9 +534,9 @@ export function OverlayReconstruction({ sessionId, onNext }: OverlayReconstructi
                   return (
                     <div key={`${cell.cellId}_wp_${i}`} className="absolute group" style={{
                       left: `${wp.xPct}%`,
-                      top: `${bboxPct.y}%`,
+                      top: `${wp.yPct}%`,
                       width: `${wp.wPct}%`,
-                      height: `${bboxPct.h}%`,
+                      height: `${wp.hPct}%`,
                     }}>
                       <input
                         id={`cell-${cell.cellId}`}

admin-lehrer/components/ocr-overlay/usePixelWordPositions.ts

@@ -4,6 +4,8 @@ import type { GridCell } from '@/app/(admin)/ai/ocr-overlay/types'
 export interface WordPosition {
   xPct: number
   wPct: number
+  yPct: number
+  hPct: number
   text: string
   fontRatio: number
 }
@@ -192,6 +194,8 @@ export function usePixelWordPositions(
             wordPos.push({
               xPct: cell.bbox_pct.x + (cl.start / cw) * cell.bbox_pct.w,
               wPct: ((cl.end - cl.start + 1) / cw) * cell.bbox_pct.w,
+              yPct: cell.bbox_pct.y,
+              hPct: cell.bbox_pct.h,
               text: groups[gi],
               fontRatio,
             })
@@ -209,6 +213,8 @@ export function usePixelWordPositions(
           wordPos.push({
             xPct: cell.bbox_pct.x + (widest.start / cw) * cell.bbox_pct.w,
             wPct: ((widest.end - widest.start + 1) / cw) * cell.bbox_pct.w,
+            yPct: cell.bbox_pct.y,
+            hPct: cell.bbox_pct.h,
             text: cell.text.trim(),
             fontRatio,
           })

admin-lehrer/components/ocr-overlay/useSlideWordPositions.ts

@@ -4,6 +4,8 @@ import type { GridCell } from '@/app/(admin)/ai/ocr-overlay/types'
 export interface WordPosition {
   xPct: number
   wPct: number
+  yPct: number
+  hPct: number
   text: string
   fontRatio: number
 }
@@ -66,6 +68,8 @@ export function useSlideWordPositions(
             const wordPos = tokens.map((t, i) => ({
               xPct: cell.bbox_pct.x + i * fallbackW,
               wPct: fallbackW,
+              yPct: cell.bbox_pct.y,
+              hPct: cell.bbox_pct.h,
               text: t,
               fontRatio: 1.0,
             }))
@@ -77,6 +81,8 @@ export function useSlideWordPositions(
           const wordPos: WordPosition[] = boxes.map(box => ({
             xPct: (box.left / imgW) * 100,
             wPct: (box.width / imgW) * 100,
+            yPct: (box.top / imgH) * 100,
+            hPct: (box.height / imgH) * 100,
             text: box.text,
             fontRatio: 1.0,
           }))
@@ -202,6 +208,8 @@ export function useSlideWordPositions(
           wordPos.push({
             xPct: cell.bbox_pct.x + (bestX / cw) * cell.bbox_pct.w,
             wPct: (tokenW / cw) * cell.bbox_pct.w,
+            yPct: cell.bbox_pct.y,
+            hPct: cell.bbox_pct.h,
             text: tokens[ti],
             fontRatio: 1.0,
           })