P44 OCR Viewer — Move original OCR toggle to left panel, replace raster with plain text
Scope: p44-ocr-viewer.js, p44-ocr-viewer.css, p44-ocr-viewer.html. Remove horizontal split pane entirely, replace with left panel toggle.

PART 1 — HTML (p44-ocr-viewer.html)
Remove the split button from the right panel header:
html<button id="btn-split" class="tb-btn" title="Toggle split view — shows original OCR above for reference (Pass 2 only)" style="display:none;">⊟ Split</button>
Add a toggle button to the left panel header, immediately after the zoom controls and before the page nav:
html<button id="btn-ocr-toggle" class="tb-btn" title="Toggle between page scan and original OCR text" style="display:none;">📄 OCR</button>
Remove these elements from #text-panel-body entirely:
html<div id="split-pane" style="display:none;">
  <div id="split-pane-header">ORIGINAL OCR</div>
  <div id="split-ocr-wrap">
    <div id="split-line-numbers"></div>
    <div id="split-ocr-output"></div>
  </div>
</div>
<div id="split-divider" style="display:none;"></div>
Add a new OCR text overlay div inside #image-panel-body, immediately after the pdf-container div:
html<div id="ocr-overlay-panel" style="display:none;"></div>

PART 2 — CSS (p44-ocr-viewer.css)
Remove all rules for:

#split-pane
#split-pane-header
#split-ocr-wrap
#split-line-numbers
#split-ocr-output
#split-divider
#text-panel-body.split-active
.split-active

Add at the end of the file:
css/* ── OCR overlay panel (replaces raster in left panel) ───────── */
#ocr-overlay-panel {
display: none;
position: absolute;
inset: 0;
overflow-y: auto;
background: var(--surface);
padding: 20px 24px;
font-size: 13px;
line-height: 1.8;
color: var(--text);
font-family: 'Georgia', 'Times New Roman', serif;
white-space: pre-wrap;
word-break: break-word;
z-index: 10;
}
Also ensure #image-panel-body has position: relative — add it to the existing rule if not already present:
css#image-panel-body {
position: relative;
}

PART 3 — JS (p44-ocr-viewer.js)
3a — Remove all split pane code
Remove these DOM refs:
javascriptconst btnSplit       = document.getElementById('btn-split');
const splitPane      = document.getElementById('split-pane');
const splitDivider   = document.getElementById('split-divider');
const splitOcrOutput = document.getElementById('split-ocr-output');
const splitLineNums  = document.getElementById('split-line-numbers');
Remove state.splitMode and state.splitRatio from the state object.
Remove these functions entirely:

buildSplitLineNumbers()
updateSplitLineNumbers()
applySplitRatio()
resetSplitSizing()
startSplitResize()
showSplitPane()
hideSplitPane()
toggleSplit()
getWrapMeasureEl()
buildWrappedLineNumbers()
parseLineHeightPx()

Remove these event listeners:
javascriptbtnSplit.addEventListener('click', toggleSplit);
splitDivider.addEventListener('mousedown', startSplitResize);
Remove from the resize event listener the split mode block:
javascriptif (state.splitMode) {
applySplitRatio(state.splitRatio || 0.5);
const pageNum = state.currentPage;
const corr = state.corrections && state.corrections[pageNum];
const originalText = (corr && corr.original) || state.ocrPages[pageNum] || '';
updateSplitLineNumbers(originalText);
}
Remove from goToPage():
javascriptif (state.splitMode) showSplitPane(n);
Remove from showOCRPage():
javascriptif (state.splitMode) showSplitPane(pageNum);
Remove from applyRole() all references to btnSplit, state.splitMode, hideSplitPane().
3b — New DOM refs
Add:
javascriptconst btnOcrToggle     = document.getElementById('btn-ocr-toggle');
const ocrOverlayPanel  = document.getElementById('ocr-overlay-panel');
Add to state object:
javascriptocrOverlay: false,
3c — showOCROverlay(pageNum)
Add this new function:
javascriptfunction showOCROverlay(pageNum) {
const corr         = state.corrections && state.corrections[pageNum];
const originalText = (corr && corr.original) || state.ocrPages[pageNum] || '';

ocrOverlayPanel.innerHTML =
'<pre style="white-space:pre-wrap;font-family:inherit;font-size:13px;' +
'line-height:1.8;color:var(--text);margin:0;">' +
escH(originalText) + '</pre>';

ocrOverlayPanel.style.display = 'block';
pdfContainer.style.display    = 'none';
imagePlaceholder.style.display = 'none';
}
3d — hideOCROverlay()
Add this new function:
javascriptfunction hideOCROverlay() {
ocrOverlayPanel.style.display  = 'none';
if (state.mode === 'pdf') {
pdfContainer.style.display   = 'inline-block';
} else {
imagePlaceholder.style.display = 'flex';
}
}
3e — toggleOCROverlay()
Add this new function:
javascriptfunction toggleOCROverlay() {
state.ocrOverlay = !state.ocrOverlay;
btnOcrToggle.classList.toggle('active', state.ocrOverlay);

if (state.ocrOverlay) {
showOCROverlay(state.currentPage);
} else {
hideOCROverlay();
}
}
Add event listener:
javascriptbtnOcrToggle.addEventListener('click', toggleOCROverlay);
3f — goToPage()
Add after if (state.editMode) exitEditMode();:
javascript  if (state.ocrOverlay) showOCROverlay(n);
3g — showOCRPage()
Add after updateCorrectionIndicator(pageNum):
javascript  if (state.ocrOverlay) showOCROverlay(pageNum);
3h — applyRole()
In the pass2 branch add:
javascript  btnOcrToggle.style.display = 'inline-block';
In the pass1 branch add:
javascript  btnOcrToggle.style.display = 'none';
state.ocrOverlay = false;
hideOCROverlay();

VERIFICATION CHECKLIST:

Pass 1 role: OCR toggle button not visible in left panel header
Pass 2 role: OCR toggle button visible in left panel header
Clicking OCR toggle: raster scan disappears, plain text original OCR fills the left panel, button highlights active
Clicking OCR toggle again: plain text disappears, raster scan returns
Navigating to a new page while OCR overlay is on: overlay updates to new page's original OCR, stays visible
Switching from Pass 2 to Pass 1 while overlay is on: overlay closes, scan returns
No horizontal split pane anywhere in the UI
Editor (right panel) unchanged — line numbers, textarea, all flags working as before