chore(combo-box): trim review-narrative comments in focusSelectedItem

Drop comments that explain choices made during the PR rather than
non-obvious WHY of the resulting code. Historical context (why the
microtask poll, why the connector holds the flag, full close-time
reset rationale) moved to PR #9194.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: DiegoCardoso

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/main/java/com/vaadin/flow/component/combobox/ComboBox.java

@@ -421,11 +421,8 @@ public void setOverlayWidth(float width, Unit unit) {
      */
     public void setFocusSelectedItem(boolean focusSelectedItem) {
         this.focusSelectedItem = focusSelectedItem;
-        // The connector's setFocusSelectedItem becomes available only once
-        // initLazy has run. Both this call and initLazy are queued via
-        // executeJs, but on the first attach there's no guarantee initLazy
-        // runs first. Poll via microtask until $connector is ready instead
-        // of relying on runBeforeClientResponse ordering.
+        // $connector is registered during initLazy. Poll via microtask
+        // until it's available so attach order isn't load-bearing.
         runBeforeClientResponse(ui -> getElement().executeJs(
                 "const apply = (val) => {" + "  if (this.$connector) {"
                         + "    this.$connector.setFocusSelectedItem(val);"

vaadin-combo-box-flow-parent/vaadin-combo-box-flow/src/main/resources/META-INF/resources/frontend/comboBoxConnector.js

@@ -334,9 +334,7 @@ window.Vaadin.Flow.comboBoxConnector.initLazy = (comboBox) => {
   // Prevent setting the custom value as the 'value'-prop automatically
   comboBox.addEventListener('custom-value-set', (e) => e.preventDefault());
 
-  // Feature flag for the focus-selected-item behavior. Set from the Java side
-  // via `comboBox.$connector.setFocusSelectedItem(value)` so it doesn't need
-  // to live as an element property the web component would otherwise ignore.
+  // Set from the Java side via `comboBox.$connector.setFocusSelectedItem(value)`.
   let focusSelectedItemEnabled = false;
   comboBox.$connector.setFocusSelectedItem = (value) => {
     focusSelectedItemEnabled = !!value;
@@ -421,23 +419,13 @@ window.Vaadin.Flow.comboBoxConnector.initLazy = (comboBox) => {
 
   comboBox.addEventListener('vaadin-combo-box-dropdown-opened', resolveFocusSelectedItem);
 
-  // Arm a DataCommunicator reset when the dropdown closes with
-  // focusSelectedItem enabled. On the next open, the feature scrolls to the
-  // selected item's position — the same viewport range the server last
-  // sent — and the server would no-op the fetch, leaving pending callbacks
-  // unresolved. Forcing a reset on the next setViewportRange RPC ensures
-  // the server re-sends data for the requested range.
-  //
-  // The reset also re-keys items via the data communicator's normal
-  // passivate-and-unregister flow — items outside the post-reset active
-  // range have their KeyMapper entries removed and get fresh keys when
-  // re-fetched. Cached pages in the connector and the data-provider
-  // controller would then hold items with stale keys that no longer match
-  // the freshly-keyed selectedItem, breaking selection highlighting (and
-  // leaving them as targets for the focusSelectedItem RPC's scrollToIndex
-  // when it sees a real item at the resolved index but with a stale key).
-  // Wipe all client-side cache state on close so the next open populates
-  // from the post-reset server data with current keys.
+  // On close with focusSelectedItem on, arm a DataCommunicator reset and
+  // wipe all client-side cache. The next open scrolls to the same viewport
+  // range the server last sent, which would otherwise be a no-op fetch and
+  // leave pending callbacks unresolved. The reset also re-keys items
+  // outside the post-reset active range; cached pages holding the old keys
+  // would no longer match the freshly-keyed selectedItem, breaking the
+  // resolveSelectedItemIndex → scrollToIndex flow.
   comboBox.addEventListener('opened-changed', (e) => {
     if (e.detail.value === false && focusSelectedItemEnabled && comboBox.selectedItem) {
       serverFacade.needsDataCommunicatorReset();