Merge remote-tracking branch 'origin/main' into arpeggio

Patch deltas on existing rows now swap just the affected element via
replaceWith() instead of tearing down and rebuilding the entire
transcript. Stops the visible flash and preserves text selection.

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

web/src/structured.ts

@@ -551,6 +551,19 @@ export function createStructuredConnection(
           rows.push(delta.row);
         } else {
           rows[i] = delta.row;
+          // Surgical DOM swap: replace just this row's element instead of
+          // tearing down and rebuilding the entire transcript, which causes
+          // visible flashing and breaks text selection.
+          const oldEl = rowEls.get(delta.row.id);
+          if (oldEl) {
+            const newEl = buildRowElement(delta.row);
+            if (newEl) {
+              oldEl.replaceWith(newEl);
+              rowEls.set(delta.row.id, newEl);
+            }
+            syncAvailableCommands();
+            return;
+          }
         }
       } else {
         const i = rowIndex.get(delta.id);