Plug three holes in Servo input forwarding

1. Scroll no longer wipes keyboard focus. Servo holds DOM focus across
   wheel events; the shell was clearing keyboard_focus and typed_texts
   on every scroll, so a focused input went deaf the moment the user
   scrolled. Scroll still drops the buffered click point because that
   coordinate is captured against the pre-scroll viewport.

2. Mouse-down hands focus to the shell's root focus handle (in
   addition to mouse-up's existing click forwarding). The user can now
   start typing the moment they press the page, instead of having to
   first complete a click round-trip to escape the omnibar's focus.

3. Sidecar hover() honors the requesting webview_id instead of
   defaulting to the first webview in the map, so multi-tab sidecars
   no longer pipe every hover into tab #1.

crates/ely_app/src/shell/web_surface.rs

@@ -137,9 +137,13 @@ impl WebSurfaceStore {
             .entry(tab_id.clone())
             .and_modify(|current| *current = current.combined_with(delta))
             .or_insert(delta);
+        // Drop any buffered click — its viewport coordinates were
+        // captured against the pre-scroll page, so applying it after
+        // the scroll would land on the wrong DOM element. Keep
+        // `keyboard_focus` and `typed_texts` though: Servo maintains
+        // its own DOM focus across scrolls, so a focused input keeps
+        // accepting the user's keystrokes after they wheel-scroll.
         self.click_points.remove(tab_id);
-        self.typed_texts.remove(tab_id);
-        self.keyboard_focus = None;
         true
     }