fix: Slide-Modus Scale-Berechnung auf Ink-Span statt Ink-Count

totalInk zaehlte nur dunkle Pixel-Spalten (Striche), ignorierte
Luecken zwischen Buchstaben. Scale war dadurch viel zu klein,
Schrift unlesbar. Jetzt wird der Ink-Span (erstes bis letztes
dunkles Pixel) als Referenz fuer die Textbreite verwendet.

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

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

@@ -129,16 +129,23 @@ export function useSlideWordPositions(
         const spaceWidth = ctx.measureText(' ').width
         const totalTextW = tokenWidths.reduce((a, b) => a + b, 0) + (tokens.length - 1) * spaceWidth
 
-        // Scale factor: how much to scale reference measurements to cell pixels
+        // Scale factor: map measured text width → pixel width on image.
-        // We use the total ink coverage as reference for total text width.
+        // Use the total INK SPAN (first dark pixel to last dark pixel),
-        let totalInk = 0
+        // not the count of dark columns.  Text characters have gaps between
-        for (let x = 0; x < cw; x++) totalInk += ink[x]
+        // strokes, so counting only dark pixels gives a much-too-small scale.
+        let firstInk = -1, lastInk = -1
+        for (let x = 0; x < cw; x++) {
+          if (ink[x]) {
+            if (firstInk < 0) firstInk = x
+            lastInk = x
+          }
+        }
 
-        // If almost no ink, fall back to centering
+        // If almost no ink, skip
-        if (totalInk < 3) continue
+        if (firstInk < 0 || lastInk <= firstInk) continue
 
-        // The scale maps measured text width → pixel width on the image
+        const inkSpan = lastInk - firstInk + 1
-        const scale = Math.min(totalInk / totalTextW, cw / totalTextW)
+        const scale = inkSpan / totalTextW
 
         // --- Slide each token from left to right ---
         const wordPos: WordPosition[] = []