feat(mdviewer): highlight specific table cell based on CM column

Count pipe characters before CM cursor position to determine the
table column index. Send tableCol with MDVIEWR_SCROLL_TO_LINE so
the viewer highlights the exact cell in the row, not just the first
cell with the matching source line.

Author: abose

src-mdviewer/src/bridge.js

@@ -932,13 +932,12 @@ function _getSourceLineFromElement(el) {
 }
 
 function handleScrollToLine(data) {
-    const { line, fromScroll } = data;
+    const { line, fromScroll, tableCol } = data;
     if (line == null) return;
 
     const viewer = document.getElementById("viewer-content");
     if (!viewer) return;
 
-
     const elements = viewer.querySelectorAll("[data-source-line]");
     let bestEl = null;
     let bestLine = -1;
@@ -952,6 +951,15 @@ function handleScrollToLine(data) {
 
     if (!bestEl) return;
 
+    // For table cells: if tableCol is specified, find the specific cell in the row
+    if (tableCol != null && bestEl.closest("tr")) {
+        const tr = bestEl.closest("tr");
+        const cells = tr.querySelectorAll("td, th");
+        if (tableCol < cells.length) {
+            bestEl = cells[tableCol];
+        }
+    }
+
     const container = document.getElementById("app-viewer");
     if (!container) return;
     const containerRect = container.getBoundingClientRect();

src/extensionsIntegrated/Phoenix-live-preview/MarkdownSync.js

@@ -567,10 +567,21 @@ define(function (require, exports, module) {
             return;
         }
         // CM5 cursor line is 0-based; source lines in markdown are 1-based
-        const line = cm.getCursor().line + 1;
+        const cursor = cm.getCursor();
+        const line = cursor.line + 1;
+        // For table rows, determine column by counting | before cursor
+        const lineText = cm.getLine(cursor.line) || "";
+        let tableCol = null;
+        if (lineText.trim().startsWith("|")) {
+            const beforeCursor = lineText.substring(0, cursor.ch);
+            // Count pipe characters (column separators) — first | is before col 0
+            const pipes = (beforeCursor.match(/\|/g) || []).length;
+            tableCol = Math.max(0, pipes - 1);
+        }
         iframeWindow.postMessage({
             type: "MDVIEWR_SCROLL_TO_LINE",
-            line: line
+            line: line,
+            tableCol: tableCol
         }, "*");
     }