fix(browser): Keep the first element name captured for an interaction

The INP element-name cache is keyed by the rounded event timestamp and every event of one
interaction shares that timestamp, so the last write won. When a handler swaps out the
element under the cursor, the browser then fires `pointerover`/`mouseover` for the new
element carrying that same timestamp, and those overwrote the cached name with the
post-mutation DOM. An INP span for a click that navigated away was named after the new body
rather than the element that was clicked.

Keeping the first name pins the entry to the element actually interacted with. Chromium 141
happened to round the follow-up events to a different millisecond, which is why this only
surfaced on a newer browser.

Author: logaretm

packages/browser-utils/src/web-vitals/inp.ts

@@ -84,6 +84,14 @@ export function registerInpInteractionListener(): void {
     const elementName = htmlTreeAsString(target);
     const timestamp = Math.round(event.timeStamp);
 
+    // Every event of one interaction shares a timestamp, and so do the `pointerover`/`mouseover`
+    // the browser fires afterwards when a handler swaps out the element under the cursor. Those
+    // arrive last and describe the new DOM, so keeping the first name is what pins the entry to the
+    // element that was actually interacted with.
+    if (ELEMENT_NAME_TIMESTAMP_MAP.has(timestamp)) {
+      return;
+    }
+
     // Store the element name by timestamp so we can match it with the PerformanceEntry
     ELEMENT_NAME_TIMESTAMP_MAP.set(timestamp, elementName);