feat(dees-table): add configurable cell flash comparison and border highlight mode

ts_web/elements/00group-dataview/dees-table/dees-table.ts

@@ -695,6 +695,7 @@ export class DeesTable<T> extends DeesElement {
                               this.__editingCell?.rowId === rowId &&
                               this.__editingCell?.colKey === editKey;
                             const isFlashing = !!flashSet?.has(editKey);
+                            const useFlashBorder = isFlashing && !!col.flashBorder;
                             const cellClasses = [
                               isEditable ? 'editable' : '',
                               isFocused && !isEditing ? 'focused' : '',
@@ -702,8 +703,13 @@ export class DeesTable<T> extends DeesElement {
                             ]
                               .filter(Boolean)
                               .join(' ');
+                            const flashClass = isFlashing
+                              ? useFlashBorder
+                                ? 'innerCellContainer flashing-border'
+                                : 'innerCellContainer flashing'
+                              : 'innerCellContainer';
                             const innerHtml = html`<div
-                              class=${isFlashing ? 'innerCellContainer flashing' : 'innerCellContainer'}
+                              class=${flashClass}
                             >
                               ${isEditing ? this.renderCellEditor(itemArg, col) : content}
                             </div>`;
@@ -1362,6 +1368,7 @@ export class DeesTable<T> extends DeesElement {
 
     const effectiveColumns = this.__getEffectiveColumns();
     const visibleCols = effectiveColumns.filter((c) => !c.hidden);
+    const colByKey = new Map<string, Column<T>>(visibleCols.map((c) => [String(c.key), c]));
     const nextSnapshot = new Map<string, Map<string, unknown>>();
     const newlyFlashing = new Map<string, Set<string>>();
 
@@ -1376,7 +1383,26 @@ export class DeesTable<T> extends DeesElement {
       const prevCells = this.__prevSnapshot?.get(rowId);
       if (!prevCells) continue; // new row — not an "update"
       for (const [colKey, nextVal] of cellMap) {
-        if (prevCells.get(colKey) !== nextVal) {
+        const prevVal = prevCells.get(colKey);
+
+        // Look up the column definition for flash options.
+        const colDef = colByKey.get(colKey);
+
+        // Determine whether the cell changed.
+        let changed: boolean;
+        if (colDef?.flashCompare) {
+          // Explicit custom comparator — caller decides.
+          changed = colDef.flashCompare(prevVal, nextVal);
+        } else if (nextVal !== null && nextVal !== undefined && typeof nextVal === 'object') {
+          // Non-primitive (TemplateResult, object, array, etc.) — skip by
+          // default. Custom renderings don't benefit from the text-color
+          // flash and reference inequality causes false positives.
+          changed = false;
+        } else {
+          changed = prevVal !== nextVal;
+        }
+
+        if (changed) {
           // Don't flash the cell the user is actively editing.
           if (
             this.__editingCell &&