Add mouse hover tracking across the Servo input pipeline

Without continuous MouseMove events, Servo never updates hover state:
no cursor changes over links, no :hover CSS effects, no mouseenter
JavaScript events. The web page appears completely non-interactive.

Track mouse position from GPUI on_mouse_move through the full IPC
pipeline to Servo. Hover position is included with each ensure
request so Servo updates hover state at frame rate (~60fps).

crates/ely_app/src/shell/web_surface_state.rs

@@ -1,10 +1,8 @@
 use ely_domain::TabId;
 
-use crate::services::servo_sidecar::{ServoSidecarClient, SidecarSnapshotRequest};
-
 use super::{
     web_surface_frame::WebSurfaceFrame,
-    web_surface_geometry::{WebSurfaceClickPoint, WebSurfaceScrollOffset, WebSurfaceSize},
+    web_surface_geometry::{WebSurfaceClickPoint, WebSurfaceScrollOffset},
 };
 
 pub(super) struct WebSurfaceScrollState {
@@ -40,60 +38,17 @@ pub(super) struct WebSurfaceTextInputState {
     pub(super) text: String,
 }
 
-#[derive(Clone, Copy)]
-pub(super) struct WebSurfaceStateKey<'a> {
-    pub(super) requested_url: &'a str,
-    pub(super) size: WebSurfaceSize,
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub(super) struct WebSurfacePendingInput {
     pub(super) scroll_offset: WebSurfaceScrollOffset,
-    pub(super) zoom_percent: u16,
-    pub(super) click_point: Option<WebSurfaceClickPoint>,
-    pub(super) typed_text: Option<&'a str>,
-}
-
-pub(super) enum WebSurfaceClient {
-    Ready(ServoSidecarClient),
-    Unavailable(String),
-}
-
-impl WebSurfaceClient {
-    pub(super) fn new() -> Self {
-        match ServoSidecarClient::new() {
-            Ok(client) => Self::Ready(client),
-            Err(error) => Self::Unavailable(error.to_string()),
-        }
-    }
-}
-
-pub(super) struct WebSurfaceRequest {
-    pub(super) tab_id: TabId,
-    pub(super) requested_url: String,
-    pub(super) size: WebSurfaceSize,
-    pub(super) scroll_offset: WebSurfaceScrollOffset,
-    pub(super) zoom_percent: u16,
+    pub(super) scroll_delta: Option<super::web_surface_geometry::WebSurfaceScrollDelta>,
     pub(super) click_point: Option<WebSurfaceClickPoint>,
+    pub(super) hover_point: Option<WebSurfaceClickPoint>,
     pub(super) typed_text: Option<String>,
-    pub(super) client: ServoSidecarClient,
-    pub(super) snapshot_request: SidecarSnapshotRequest,
 }
 
 pub(super) enum WebSurfaceState {
-    Loading {
-        requested_url: String,
-        size: WebSurfaceSize,
-        scroll_offset: WebSurfaceScrollOffset,
-        zoom_percent: u16,
-        click_point: Option<WebSurfaceClickPoint>,
-        typed_text: Option<String>,
-        previous_frame: Option<WebSurfaceFrame>,
-    },
+    Loading { requested_url: String, previous_frame: Option<WebSurfaceFrame> },
     Ready(WebSurfaceFrame),
-    Failed {
-        requested_url: String,
-        size: WebSurfaceSize,
-        scroll_offset: WebSurfaceScrollOffset,
-        zoom_percent: u16,
-        click_point: Option<WebSurfaceClickPoint>,
-        typed_text: Option<String>,
-        message: String,
-    },
+    Failed { message: String },
 }